Leisha This is a long article and was inspired because I was working with some workshop participants and friends and I wanted to go deeper into understanding the thyroid and most especially, Hashimotos.
Over the years I have worked with many people diagnosed with Hashimoto’s thyroiditis and I did not have a complete understanding myself. Most have been women, which reflects the fact that Hashimoto’s affects women far more often than men. Men certainly develop the condition as well, but because women represent the majority of those seeking help, much of what I have observed has come through working alongside them as they try to understand what has changed within their bodies.
Many arrive carrying years of unanswered questions. They have been told that their thyroid is under-active, that their immune system is attacking the gland, and that thyroid medication will likely become part of their future. Some feel better after beginning medication, while others continue to struggle with fatigue, digestive problems, brain fog, poor sleep, weight gain, cold hands and feet, thinning hair, anxiety, or the overwhelming feeling that they simply no longer recognize themselves.
Thyroid hormone replacement can produce side effects. Side effects are listed as palpitations, a rapid or irregular heartbeat, chest pain, anxiety, nervousness, tremors, insomnia, headaches, excessive sweating, heat intolerance, increased appetite, weight loss, diarrhea, muscle weakness, menstrual irregularities, and hair thinning. Long-term concerns may include mineral dysregulation, reduced bone density, osteoporosis, increased fracture risk, atrial fibrillation, and added cardiovascular strain.
One of the challenges is that many of these side effects closely resemble the symptoms of thyroid disease itself, making it difficult to determine whether a person’s symptoms are due to the medication, the underlying condition, or changes in thyroid hormone levels.
One question we should ask: “Why is my body is attacking itself?”
I have never been satisfied with simply knowing what is happening. I have always wanted to understand why it is happening. This question has guided much of my work, not only in human health but also in the study of living systems. Whether I am looking through a microscope at living blood, examining the biology within healthy compost, or studying the remarkable complexity of the soil food web, I rarely find that nature behaves without reason. Every response has a history and every change develops within a context. The visible result is often only the final chapter of a story that has been unfolding quietly for months or even years.
The human body has taught me much the same lesson. The immune system is one of the most intelligent biological systems we possess. Every second of every day it evaluates an extraordinary amount of information. It distinguishes between tissues that belong within the body and those that do not. It identifies viruses, parasites, damaged cells, foreign proteins, and countless other potential threats while leaving billions of healthy cells untouched. This remarkable ability to distinguish self from non-self is known as immune tolerance, and without it we simply could not survive. I wrote a book about this to help people understand the immune system as compared to a garden in nature
When that tolerance begins to change, I do not believe the immune system has suddenly become confused or irrational. I believe it is responding to information. The real question is not why the immune system has become aggressive, but what information it has been receiving that gradually altered its behaviour.
Looking at Hashimoto’s through that lens changes the conversation completely. Instead of seeing the thyroid as a gland that has somehow failed, we begin asking what has changed within the body’s internal environment. What influences have shaped the immune system over time? What conversations have been taking place between the digestive tract, the microbiome, hormones, nutrients, the nervous system, and the thyroid itself? Why has the immune system begun recognizing a familiar tissue differently than it once did?
These questions lead us away from seeing Hashimoto’s as an isolated thyroid disorder and toward understanding it as part of a much larger biological story.
The Thyroid May Not Be Where the Story Begins
One of the greatest lessons I have learned from studying ecology and nature is that the most obvious problem is rarely the place where the problem began.
When someone walks into a neglected field, they usually notice the weeds first. It is easy to assume the weeds are the cause of the problem because they are the most visible part of the landscape. Yet anyone who spends time studying soil soon realizes that the weeds are responding to conditions that already existed beneath the surface. Changes in soil structure, mineral availability, organic matter, moisture, and microbial diversity all influence which plants eventually appear. The weeds are not creating the imbalance. They are responding to it.
I often think about Hashimoto’s in much the same way. The thyroid is where the immune response becomes visible, but it may not be where the story actually began. The inflammation, the elevated antibodies, and the gradual decline in thyroid function may represent the body’s response to changes that have been developing quietly for years.
That perspective does not diminish the importance of the thyroid. Rather, it encourages us to widen our view. Instead of asking only how to support thyroid hormone production, we begin exploring the systems that educate and regulate the immune response itself.
This is where the science becomes particularly fascinating.
Understanding What Hashimoto’s Really Is
Hashimoto’s thyroiditis is generally classified as an autoimmune disease because the immune system begins targeting proteins found within the thyroid gland. It is the most common cause of hypothyroidism in countries where iodine intake is considered adequate, and it is also the most common autoimmune disease worldwide.
The condition was first described in 1912 by the Japanese physician Hakaru Hashimoto, who observed that affected thyroid glands were densely infiltrated with lymphocytes, the white blood cells responsible for coordinating many aspects of the immune response. More than one hundred years later, those same immune cells remain central to our understanding of the disease.
Although Hashimoto’s is often described as a thyroid disorder, it is more accurate to think of it as an immune disorder that happens to involve the thyroid. The gland becomes the target, but it is the immune system that initiates the response.
Two groups of immune cells play particularly important roles:
- The first are T lymphocytes, commonly called T cells. These cells move into the thyroid gland and gradually destroy the follicular cells responsible for producing thyroid hormones. Current evidence suggests that these T cells are responsible for most of the tissue damage that occurs as the disease progresses.
- The second group are B lymphocytes, or B cells. Rather than directly attacking thyroid tissue, B cells produce antibodies against thyroid proteins. These antibodies are not believed to cause most of the damage themselves, but they are extremely useful because they allow us to measure the activity of the immune response.
The two antibodies most commonly measured are thyroid peroxidase antibodies (TPO antibodies) and thyroglobulin antibodies (TgAb). Thyroid peroxidase is an enzyme that helps attach iodine to the amino acid tyrosine during the production of thyroid hormones. Approximately ninety to ninety-five percent of people with Hashimoto’s have elevated TPO antibodies. Thyroglobulin is the large storage protein upon which thyroid hormones are assembled before being released into the circulation. Antibodies against thyroglobulin are present in approximately sixty to eighty percent of people living with the condition.
One point that is often misunderstood is that these antibodies are primarily markers of immune activity rather than the primary cause of thyroid destruction. The ongoing injury to the gland is driven mainly by the T-cell response occurring within the thyroid tissue itself. Nevertheless, antibody levels remain valuable because they often provide insight into how active the autoimmune process has become and whether that activity is increasing, remaining stable, or gradually settling over time.
Another important aspect of Hashimoto’s is that it develops slowly. The immune system may begin producing antibodies years before thyroid hormone production is noticeably affected. During this period the thyroid often compensates remarkably well, and routine thyroid hormone tests may still appear completely normal. Some people remain in this early stage for many years, while others progress more rapidly. Eventually, enough thyroid tissue may be damaged that hormone production begins to decline, leading to the symptoms commonly associated with hypothyroidism.
This gradual progression explains why so many people say they never felt truly well for years before finally receiving a diagnosis. Looking back, they often recognize a slow accumulation of symptoms that never seemed important on their own but, together, painted a very different picture.
It is also one of the reasons I believe we need to look beyond the thyroid itself. If the immune system has been changing long before thyroid function begins to fail, then the processes influencing that immune response deserve just as much attention as the thyroid gland.
The thyroid is particularly sensitive because it concentrates minerals, depends upon finely regulated enzyme systems, and responds continuously to hormonal signals. Reducing unnecessary environmental burden may not reverse Hashimoto’s on its own, but it removes one more source of physiological stress that the body no longer needs to manage.
At the same time, replacing thyroid hormone does not replace the work of understanding why the immune system began responding to the thyroid. Levothyroxine provides T4, but the body must still convert that hormone into T3. That conversion depends upon healthy digestion, adequate selenium, zinc, iron, liver function, microbial activity, and an environment that is not overwhelmed by chronic inflammation or stress.
The longer I study both the human microbiome and the soil food web, the more difficult it becomes to separate them in my mind. Healthy ecosystems are built upon relationships. Billions of microorganisms communicate continuously, recycle nutrients, regulate minerals, build structure, and maintain resilience throughout the entire community. When those relationships begin to break down, the whole ecosystem changes. The human body behaves no differently.
Hashimoto’s has reinforced this lesson for me over and over again. I no longer see it as a thyroid that has failed or an immune system that has simply become confused. I see a remarkably intelligent body responding to years of changing information. Some of that information may have come from the digestive tract. Some may have come from the microbiome, nutrient depletion, hormonal changes, chronic stress, environmental exposures, or previous infections. The thyroid has simply become the place where those accumulated conversations have become visible.
I cannot promise that every thyroid will fully recover. Some people will continue to need thyroid hormone replacement, and it may remain an important part of supporting their health. What I have seen, however, is that many people regain far more than they believed possible when the focus shifts from treating the thyroid alone to restoring the entire terrain. Digestion often improves. Energy slowly returns, sleep becomes deeper and thinking becomes clearer. Antibody levels may gradually decline and the nervous system becomes calmer. The body begins responding differently because it is receiving different information.
Perhaps that is the most important lesson Hashimoto’s has taught me. The diagnosis is not the end of the story.
In many ways, it is simply the point where we begin asking better questions. When we stop asking only what is wrong with the thyroid and begin asking why the immune system has chosen this response, we begin seeing the body as a living ecosystem rather than a collection of isolated organs. That change in perspective has transformed the way I understand health, and it continues to shape the way I work with every person who walks through my door.
Why Does the Immune System Lose Tolerance?
If Hashimoto’s begins with a change in immune tolerance, the next question becomes obvious. What causes the immune system to stop recognizing thyroid tissue as part of the body it has protected for decades?
Despite years of research, there is no single answer, and I suspect there never will be. Human biology is rarely driven by one event. More often, health reflects the combined influence of genetics, nutrition, microbial life, environmental exposures, hormones, emotional wellbeing, and the countless experiences that shape us throughout our lives. The immune system is continually integrating information from all of these sources before deciding how to respond.
This helps explain why no two people experience Hashimoto’s in exactly the same way. Two individuals may carry the same diagnosis while arriving there through very different pathways. One may have struggled with digestive problems for years, another may have noticed changes after pregnancy, while someone else recalls a significant illness or prolonged period of stress before symptoms gradually appeared. The destination may look similar, but the journey often differs.
Understanding those individual pathways is important because it reminds us that the immune system does not operate in isolation. It is constantly learning, adapting, and responding to the world within and around us.
Genetics Create Susceptibility, Not Certainty
There is little doubt that genetics influence the development of Hashimoto’s. The condition often appears within families, and researchers have identified several genes that influence how the immune system recognizes proteins and regulates inflammation. Variations involving HLA genes, PTPN22, CTLA-4, and several other immune-related genes are more common among people living with autoimmune thyroid disease.
These discoveries have helped explain why some individuals appear more susceptible than others, but they have also highlighted something equally important. Genetics alone do not determine who develops Hashimoto’s.
Studies involving identical twins provide one of the clearest examples. If genes alone controlled the disease, identical twins would almost always develop Hashimoto’s together because they share essentially the same DNA. Instead, studies report concordance rates of approximately thirty-eight to fifty-five percent. In other words, one twin may develop Hashimoto’s while the other never does.
That observation changes how we think about genetics. Our genes influence the way we respond to our environment, but they do not completely determine our future. Modern research into epigenetics has shown that genes can be switched on or off depending upon many different influences, including nutrition, microbial exposures, hormones, stress, sleep, physical activity, and environmental factors. The genetic blueprint may remain unchanged throughout life, but how that blueprint is expressed is remarkably dynamic.
For me, this is an encouraging way to think about chronic illness. A genetic predisposition does not mean a person is destined to develop disease. It simply means the body may be more sensitive to certain influences, making the surrounding environment even more important.
The Digestive Tract Is One of the Immune System’s Greatest Teachers
When people think about digestion, they usually think about breaking down food and absorbing nutrients. Those functions are certainly important, but they represent only part of the story. The digestive tract is also one of the body’s largest immune organs, continually teaching the immune system what belongs within the body and what does not.
Every day the intestinal lining encounters an extraordinary range of substances. Food proteins, beneficial microbes, environmental organisms, fungi, viruses, bacterial fragments, toxins, and metabolic waste all pass through this remarkable system. The immune system must decide which of these are harmless, which require tolerance, and which require protection.
This process depends upon a healthy intestinal barrier. The cells lining the intestine form a remarkably thin layer between the contents of the digestive tract and the bloodstream. These cells are connected by specialized protein structures known as tight junctions, which act rather like carefully regulated gates. Under healthy conditions they allow nutrients, water, vitamins, minerals, and other essential compounds to pass into circulation while preventing larger food proteins, bacterial fragments, and toxins from crossing the barrier.
The integrity of this barrier depends upon many factors. Adequate nutrition, healthy microbial communities, good blood supply, continual cellular repair, and balanced immune signalling all contribute to maintaining its strength. When these systems begin struggling, the barrier may become more permeable than it was designed to be.
Researchers refer to this as increased intestinal permeability, although many people know it by the term leaky gut.
The Intestinal Barrier Is Not Static
One of the major advances in our understanding of intestinal permeability came through the work of Dr. Alessio Fasano and his colleagues, who identified the important role of a protein called zonulin.
Zonulin helps regulate the opening and closing of the intestinal tight junctions. This is a completely normal process and allows the digestive tract to adjust its permeability when appropriate. Problems arise when these openings become larger or remain open longer than intended.
Several factors are known to influence zonulin production. Certain infections can stimulate its release, as can gliadin, one of the proteins found in gluten. This response occurs in everyone to some degree, but in genetically susceptible individuals the effect may be greater, allowing larger food proteins and bacterial components greater access to the immune system.
When that happens, the immune system is not behaving abnormally by responding. It is simply encountering substances that it would not normally expect to see beyond the intestinal barrier.
This does not mean every person with Hashimoto’s has increased intestinal permeability, nor does it suggest that intestinal permeability alone explains the disease. It does, however, provide one possible mechanism through which immune tolerance may gradually begin to change.
When Familiar Shapes Look the Same
One of the more fascinating concepts in immunology is known as molecular mimicry. The immune system identifies foreign proteins by recognizing their molecular structure. Occasionally, a protein produced by a microorganism or found within food shares enough structural similarity with one of our own tissues that antibodies or immune cells begin reacting with both.
This is rather like recognizing someone by their silhouette. From a distance two different people may appear remarkably similar. The closer we look, the easier they become to distinguish. The immune system faces much the same challenge when proteins resemble one another closely enough to create mistaken identity.
In Hashimoto’s, researchers have explored similarities between gliadin and thyroid proteins such as thyroid peroxidase and thyroglobulin. While this relationship does not occur in everyone, it may help explain why some individuals experience significant improvement after removing gluten from their diet.
Food is not the only possibility. The bacterium Yersinia enterocolitica, which can cause intestinal infections, has attracted considerable attention because some of its surface proteins resemble portions of the thyroid-stimulating hormone receptor. Studies have shown that antibodies directed against Yersinia may also recognize thyroid tissue, providing another possible pathway through which immune tolerance could gradually be altered.
None of these findings suggests that one food or one microorganism causes Hashimoto’s. Rather, they demonstrate how repeated exposure, genetic susceptibility, and changes in the intestinal barrier may work together over time to reshape the immune response.
The Microbiome Is Part of the Conversation
Perhaps the greatest change in biological science over the past twenty years has been our growing appreciation of the human microbiome. We now understand that the trillions of microorganisms living within us are not passive passengers. They participate in digestion, manufacture vitamins, produce signalling molecules, regulate inflammation, influence metabolism, and help educate the immune system throughout life.
One of their most important roles is helping maintain immune tolerance.
Certain intestinal bacteria ferment dietary fibre into short-chain fatty acids, particularly butyrate. This remarkable molecule provides energy for the cells lining the colon, strengthens the intestinal barrier, and supports the development of regulatory T cells. These specialized immune cells help prevent unnecessary immune activation and play an essential role in maintaining tolerance toward the body’s own tissues.
When microbial diversity begins to decline, the production of these beneficial compounds often declines as well. Research has consistently shown that people living with Hashimoto’s frequently have a different microbial community than healthy individuals. Diversity may be reduced, beneficial butyrate-producing organisms are often less abundant, and inflammatory microbial patterns become more common.
The microbiome also contributes directly to thyroid physiology. Intestinal microbes participate in nutrient metabolism, influence iodine availability, contribute to thyroid hormone metabolism, regulate estrogen recycling through the estrobolome, and communicate continuously with immune cells throughout the digestive tract. The thyroid, the microbiome, and the immune system are engaged in an ongoing conversation that cannot easily be separated into individual parts.
This is one of the reasons I find it difficult to separate human health from what I have learned studying the soil food web. Healthy soil is not sustained by one organism. It depends upon the relationships between bacteria, fungi, protozoa, nematodes, arthropods, plant roots, organic matter, minerals, water, and countless other forms of life. Diversity creates resilience because each organism contributes something that supports the whole system.
The human microbiome follows remarkably similar principles. No single microorganism creates health, yet together they build an environment that supports immune regulation, nutrient cycling, tissue repair, and resilience. As diversity declines, those relationships begin to weaken, and the entire ecosystem becomes less stable.
Perhaps this is one of the most important lessons the microbiome has taught us. Health is not created by one nutrient, one bacterium, or one organ working alone. It emerges from millions of relationships functioning together.
Understanding those relationships does not explain every case of Hashimoto’s, but it gives us a far richer understanding of why the immune system may gradually lose tolerance. It also points us toward a broader way of thinking about health, one that recognizes the immune system as part of a living ecosystem rather than an isolated defence mechanism.
The Immune System Continues to Learn Throughout Life
One of the most remarkable discoveries in modern biology is that the immune system is not fixed. It does not make one decision and continue following that path forever. Instead, it is constantly adapting to the information it receives from the body and from the environment. Every meal, every season of life, every infection, every night of sleep, and every period of physical or emotional stress contributes to the signals that help shape immune regulation.
This continual adaptation is one of the reasons autoimmune diseases are so complex. The immune system is not responding to one event in isolation. It is responding to years of accumulated experiences, many of which may seem unrelated when viewed individually. A nutrient deficiency, disrupted sleep, hormonal changes, environmental exposures, and chronic inflammation may each appear relatively small on their own. Together, however, they gradually influence how the body regulates itself.
Rather than searching for a single cause, I think it is more helpful to understand the factors that support healthy immune function throughout life. When these systems are working together, they create an internal environment that encourages resilience. When they begin to drift apart, the immune system often becomes less balanced and more reactive.
Nutrients That Support Thyroid Physiology
The thyroid is a remarkably active gland. Although small in size, it produces hormones that influence metabolism, energy production, body temperature, cardiovascular function, digestive activity, nervous system function, growth, and cellular repair throughout the body. Carrying out this work requires a continual supply of nutrients that support hormone production, antioxidant protection, and cellular communication.
One of the most important of these nutrients is selenium. The thyroid contains a higher concentration of selenium than any other organ in the body, reflecting how essential this mineral is for normal thyroid physiology. Every time thyroid hormones are produced, small amounts of hydrogen peroxide are generated as part of the manufacturing process. Under healthy conditions this presents no problem because selenium-dependent enzymes, particularly glutathione peroxidase, rapidly convert hydrogen peroxide into harmless compounds before it can damage surrounding tissue.
Selenium also supports the deiodinase enzymes responsible for converting thyroxine (T4) into triiodothyronine (T3), the biologically active thyroid hormone used by every cell in the body. Several clinical studies have shown that selenium supplementation may reduce thyroid antibody levels in some people living with Hashimoto’s, particularly when selenium intake has been low. Although responses vary between individuals, these findings highlight the importance of providing the thyroid with the nutritional support it requires rather than assuming hormone production alone tells the entire story.
Iodine remains equally essential because it forms the structural backbone of both T4 and T3. Without iodine the thyroid cannot manufacture these hormones. At the same time, research has shown that excessive iodine intake may increase autoimmune activity in susceptible individuals, particularly when selenium status is inadequate. Rather than viewing iodine as either good or bad, I think it is more accurate to see it as a nutrient that depends upon balance. Like so many aspects of biology, the relationship between iodine and selenium illustrates that nutrients rarely work independently of one another.
Iron also deserves careful consideration because thyroid peroxidase, the enzyme involved in thyroid hormone production, depends upon adequate iron stores. A person may have ferritin levels that technically fall within the laboratory reference range while still not having sufficient iron available to support optimal thyroid physiology. Vitamin A contributes to thyroid hormone receptor function, zinc participates in hormone production and receptor activity, magnesium supports hundreds of enzyme systems throughout the body, and vitamin B12 is essential for healthy nerve function, red blood cell production, and energy metabolism. Deficiencies in any of these nutrients do not automatically cause Hashimoto’s, but they can make recovery more difficult by limiting the body’s ability to regulate itself effectively.
Hormones Are Part of the Same Conversation
Hashimoto’s occurs far more frequently in women than in men, suggesting that hormones influence the way immune regulation develops. Many people first notice symptoms during periods of significant hormonal change, including pregnancy, the months following childbirth, and the years leading into menopause. These transitions place considerable demands on the endocrine and immune systems, and for some individuals they appear to reveal an underlying susceptibility that had previously remained quiet.
Estrogen plays an important role because it influences antibody production, immune cell activity, and thyroid hormone transport throughout the body. Healthy estrogen metabolism depends not only on the ovaries and liver but also on the intestinal microbiome. Certain intestinal bacteria participate in recycling estrogen through a collection of microbial genes known as the estrobolome. When microbial balance changes, estrogen metabolism may change as well, further demonstrating that the endocrine and digestive systems are closely connected.
This relationship reminds us once again that the body does not function as a collection of isolated organs. The thyroid, ovaries, liver, digestive tract, microbiome, and immune system continually influence one another through an intricate network of hormonal and biochemical communication.
The Nervous System Cannot Be Ignored
There is one area of health that I think is often underestimated when discussing autoimmune disease, and that is the influence of the nervous system.
When we experience prolonged stress, the body adapts in remarkable ways to help us survive. Hormones such as cortisol and adrenaline alter metabolism, influence immune activity, change digestive function, affect blood sugar regulation, and shift how the body distributes its resources. These responses are helpful during genuine emergencies, but they become far less beneficial when they continue for months or years without adequate recovery.
Chronic activation of the stress response may influence thyroid physiology in several ways. Elevated cortisol can reduce the conversion of T4 into T3, alter immune regulation, weaken digestive function, affect intestinal barrier integrity, disturb sleep, and contribute to changes within the microbiome. None of these effects occurs independently. Each influences the others, gradually reshaping the environment in which the immune system functions.
Many of the people I have worked with can identify periods of prolonged emotional strain before their health began changing. Sometimes it was the loss of a loved one, years of caregiving, financial uncertainty, workplace demands, unresolved trauma, or simply living for too long without adequate rest. I do not believe stress alone explains Hashimoto’s, but I do believe it can become one of the many influences that slowly alters the body’s capacity to maintain balance.
Our Modern Environment Has Changed
Human physiology evolved over thousands of years within environments that were very different from the ones we experience today. During the past century alone we have introduced thousands of synthetic chemicals into our air, water, food, and homes. Many of these compounds have been studied for their potential influence on hormone regulation, immune function, and thyroid physiology.
Heavy metals such as mercury, cadmium, and lead have all been investigated because of their ability to interfere with enzyme systems and increase oxidative stress. Endocrine-disrupting compounds, including bisphenol A (BPA), phthalates, and persistent chemicals such as PFAS, may influence hormone receptors or alter normal endocrine signalling. Agricultural chemicals and certain industrial pollutants have also been associated with changes in thyroid function in some studies.
This does not mean environmental chemicals are the primary cause of Hashimoto’s, nor does it mean everyone with the condition has experienced significant toxic exposure. It does remind us, however, that the immune system is responding within an environment that is far more chemically complex than the one in which human physiology evolved. Reducing unnecessary exposure where possible becomes one more way of supporting the body’s natural regulatory systems rather than adding to the burden they already carry.
By this point, a pattern should be emerging. Whether we are discussing nutrients, hormones, the nervous system, or environmental influences, the same principle continues to appear. No single factor explains Hashimoto’s on its own. Instead, the condition reflects the interaction of many biological systems that have gradually moved away from balance. Understanding those relationships allows us to move beyond the diagnosis itself and begin asking a more useful question: what does this particular body need in order to regain resilience?
Why the Symptoms Develop
One of the reasons Hashimoto’s can be so frustrating is that the symptoms rarely appear all at once. They often develop gradually, becoming part of everyday life so slowly that many people do not recognize how much has changed until they begin looking back. It is common to hear someone say, “I thought I was simply getting older,” or “I assumed everyone felt this tired.”
In the early stages, the thyroid often continues producing enough hormone to keep laboratory results within the normal reference range. During this period the immune system may already be active, antibodies may already be elevated, and inflammation may already be developing, yet the person may not meet the criteria for hypothyroidism. Even so, many begin noticing subtle changes in energy, mood, digestion, concentration, and resilience long before significant alterations appear on routine blood work.
As more thyroid tissue becomes affected, hormone production gradually becomes less efficient. Because thyroid hormones influence almost every cell in the body, the effects are rarely limited to one organ. Instead, metabolism begins slowing throughout multiple systems at the same time, and the symptoms that develop reflect the remarkable reach of the thyroid itself.
Why Fatigue Feels Different
Fatigue is usually the first symptom people describe, but it is rarely ordinary tiredness. Many explain that they are sleeping enough yet still wake feeling unrefreshed. Others find they can complete daily responsibilities, but only by pushing themselves through a level of exhaustion that never seems to improve with rest.
This happens because thyroid hormones regulate energy production within every cell. Inside our cells, mitochondria convert nutrients into adenosine triphosphate (ATP), the primary source of cellular energy. Thyroid hormones help regulate this process by influencing oxygen consumption, enzyme activity, and the rate at which nutrients are converted into usable energy.
When thyroid hormone activity begins to decline, energy production slows throughout the body. Muscles tire more easily, physical recovery takes longer, and even mental tasks require greater effort. This is why fatigue associated with hypothyroidism often feels deeper than simply needing another night’s sleep. The body is producing less energy at a cellular level.
Inflammation may contribute as well. The immune response itself requires considerable energy, and inflammatory cytokines released during chronic immune activation can further increase feelings of fatigue and reduce physical endurance. Many people living with autoimmune diseases describe this sensation as though the body is constantly working behind the scenes, even while they are resting.
Brain Fog and Memory Changes
One of the most common concerns I hear is difficulty thinking clearly. People often describe feeling as though their thoughts have become slower or less organized. Finding words becomes more difficult, concentrating requires greater effort, and short-term memory may seem less reliable than it once was.
The brain is one of the body’s most metabolically active organs and depends heavily on thyroid hormones for normal function. These hormones influence blood flow, glucose utilization, neurotransmitter production, and communication between nerve cells. As thyroid hormone activity declines, these processes become less efficient, leading to the collection of symptoms commonly described as brain fog.
Inflammation may further influence cognitive function. Cytokines produced during chronic immune activation can affect communication between the immune system and the brain, contributing to changes in concentration, motivation, and mood. Poor sleep, altered blood sugar regulation, and nutrient deficiencies may also contribute, reminding us that brain fog rarely has a single cause.
Weight Changes and a Slower Metabolism
Weight gain is frequently associated with hypothyroidism, yet the explanation is more complex than simply burning fewer calories.
Thyroid hormones regulate basal metabolic rate, which represents the amount of energy the body uses simply to maintain normal function. They influence body temperature, protein synthesis, fat metabolism, carbohydrate utilization, and how efficiently cells convert nutrients into energy.
As metabolism slows, calorie requirements decrease. At the same time, reduced physical energy often means people move less than they once did, even if they remain active. Fluid retention may also increase because thyroid hormones influence kidney function and the body’s ability to regulate sodium and water balance. These changes together may lead to gradual weight gain, even when dietary habits have changed very little.
Not everyone gains weight, however. Some individuals maintain a stable weight despite significant thyroid dysfunction, while others notice changes long before laboratory values become abnormal. Every person adapts differently, which is one reason symptoms alone cannot determine the severity of thyroid disease.
Feeling Cold
Many people with Hashimoto’s describe always feeling cold, even when those around them are comfortable. Hands and feet may remain cold throughout the day, and winter often becomes particularly difficult to tolerate.
Body temperature depends upon metabolism. As cells produce energy they also generate heat. When thyroid hormone activity decreases, heat production declines, making it more difficult to maintain normal body temperature. Reduced circulation may further contribute to cold hands and feet, particularly when metabolism slows throughout the cardiovascular system.
This symptom often improves gradually as thyroid physiology becomes better supported, although it may take time because every tissue in the body must slowly adapt to changing hormone availability.
Hair, Skin, and Nails
Healthy hair, skin, and nails are continually renewing tissues, requiring a constant supply of nutrients, oxygen, and energy. Thyroid hormones influence each of these processes.
Hair follicles spend longer in their resting phase when thyroid hormone activity is reduced, leading to increased shedding and slower regrowth. Skin may become dry because oil production decreases and cellular turnover slows. Nails often become brittle or grow more slowly than before.
These changes are not usually dangerous, but they can be emotionally distressing because they are so visible. Fortunately, they often improve gradually as thyroid function and nutritional status become better supported, although hair growth in particular may require several months before noticeable improvement occurs.
Digestion Slows
The digestive tract is one of the body systems most noticeably affected by reduced thyroid activity.
Normal digestion depends upon coordinated muscle contractions known as peristalsis, which move food through the stomach and intestines. Thyroid hormones help regulate this movement. As hormone activity declines, the digestive tract often becomes slower, allowing food to remain in the intestines longer than normal.
Constipation becomes one of the most common consequences of this slowing. Prolonged transit time may also alter the intestinal microbiome, increase fermentation, and influence the recycling of hormones within the digestive tract. Some people experience bloating, abdominal discomfort, or increased sensitivity to certain foods, although these symptoms are often influenced by several factors rather than thyroid physiology alone.
Because the digestive tract and immune system communicate so closely, changes in one system frequently influence the other. This relationship reinforces the importance of viewing Hashimoto’s as more than a disease affecting only one gland.
Mood and Emotional Wellbeing
The relationship between thyroid hormones and mental health has been recognized for many years. Anxiety, depression, reduced motivation, irritability, and emotional sensitivity may all occur in people living with Hashimoto’s, although the experience varies considerably from one individual to another.
Thyroid hormones influence the production and activity of several neurotransmitters, including serotonin, dopamine, and norepinephrine. They also affect blood flow within the brain and the rate at which nerve cells communicate with one another. When hormone activity declines, emotional wellbeing may change alongside physical health.
Living with a chronic illness also places emotional demands on the individual. Many people spend years searching for answers before receiving a diagnosis. Others feel dismissed because laboratory results appear normal despite ongoing symptoms. These experiences can create understandable frustration and uncertainty, making emotional support just as important as physical care.
Cholesterol, Muscles, and the Heart
The influence of thyroid hormones extends well beyond energy production.
Thyroid hormones help regulate cholesterol metabolism by increasing the number of LDL receptors in the liver. As thyroid activity declines, LDL cholesterol is removed from the bloodstream less efficiently, and cholesterol levels may gradually increase despite no significant change in diet.
Muscles may become stiff, weak, or slow to recover after activity because protein turnover and energy production both decline. Some people notice cramps or aching muscles, while others simply describe feeling physically heavier than they once did.
The heart also responds to thyroid hormones. Heart rate may slow, cardiac output may decrease, and exercise tolerance often becomes reduced. Although these changes are usually mild in early disease, they remind us that the thyroid influences virtually every organ system in the body.
No Two People Experience Hashimoto’s the Same Way
One of the reasons Hashimoto’s remains such a challenging condition is that no two people experience it in exactly the same way. Some develop symptoms gradually over many years, while others notice more rapid changes following pregnancy, illness, or another major life event. Some struggle primarily with fatigue, whereas others are affected more by digestive symptoms, anxiety, cognitive changes, or cold intolerance.
This variation should not be surprising. Every person’s genetics, microbiome, nutritional status, hormonal history, environmental exposures, and life experiences are different. The immune system is responding within a unique biological landscape, and that landscape shapes how the condition is expressed.
Understanding this has changed the way I work with people. Rather than trying to fit everyone into the same protocol, I begin by asking what pattern is emerging in front of me. The diagnosis may be the same, but the path that brought someone there, and the path back toward greater health, is rarely identical.
Looking Beyond a Single Laboratory Result
One of the challenges of Hashimoto’s is that the condition rarely fits neatly into one laboratory value. Many people are told that everything looks normal because one marker falls within the laboratory reference range, while others are understandably worried because one number has changed even though they feel relatively well. Neither situation tells the whole story.
Laboratory testing remains an important part of understanding thyroid health, but every test represents only one small piece of a much larger biological picture. No single result can explain how the immune system is behaving, how efficiently the thyroid is functioning, or how well the body is adapting to the changes taking place.
For that reason, I have always believed that laboratory findings should be interpreted alongside the person’s history, symptoms, lifestyle, nutritional status, and the broader patterns that have developed over time. Numbers are valuable, but they make far more sense when they are placed within the context of the whole person.
TSH Is Only the Beginning
The thyroid stimulating hormone (TSH) test is often the first investigation ordered when thyroid disease is suspected, and for good reason. TSH is produced by the pituitary gland and reflects how strongly the brain is signalling the thyroid to produce more hormone. As thyroid hormone production begins to decline, TSH often rises in an effort to encourage the gland to work harder.
Although this makes TSH an excellent screening tool, it was never intended to answer every question about thyroid physiology. It tells us very little about the activity of the autoimmune process, how much healthy thyroid tissue remains, or why someone may still be experiencing symptoms.
It is also important to remember that laboratory reference ranges are designed to identify disease within large populations. They do not necessarily define what is optimal for every individual. Two people with identical TSH values may feel completely different because thyroid physiology depends upon much more than one hormone signal between the pituitary gland and the thyroid.
Looking at the Whole Thyroid Picture
When a more complete assessment is needed, additional laboratory markers often provide a clearer understanding of what is taking place.
Free T4 reflects the amount of circulating thyroxine that is available to the body, while Free T3 represents the active hormone that cells use to regulate metabolism. Looking at these values together helps determine whether the thyroid is producing adequate hormone and whether sufficient active hormone is reaching the tissues.
Reverse T3 may also provide useful information in some situations, particularly when symptoms continue despite apparently satisfactory thyroid hormone levels. Reverse T3 is an inactive form of thyroid hormone that may increase during periods of prolonged physiological stress, illness, or significant inflammation. On its own, it does not diagnose disease, but when interpreted alongside other findings it may help explain why some people continue experiencing symptoms even when routine thyroid tests appear acceptable.
The autoimmune component of Hashimoto’s is followed by measuring thyroid peroxidase antibodies (TPO antibodies) and thyroglobulin antibodies (TgAb). As we discussed earlier, these antibodies are best understood as markers of immune activity rather than direct measures of thyroid function. Monitoring them over time can provide insight into whether the autoimmune response appears stable, increasing, or gradually becoming less active.
Looking Beyond the Thyroid
One lesson that Hashimoto’s has taught me is that supporting thyroid health often requires looking well beyond the thyroid itself.
Routine blood work may reveal changes in iron stores, vitamin B12, vitamin D, blood sugar regulation, cholesterol, inflammatory markers, or other aspects of physiology that influence how a person feels. None of these tests diagnoses Hashimoto’s, yet each contributes important information about the body’s overall health and resilience.
When digestive symptoms are present, further investigation may also be appropriate. In some cases this may include screening for coeliac disease, evaluating the intestinal microbiome, or assessing other aspects of digestive function. The goal is not to order as many tests as possible but to answer meaningful questions that help explain the person’s clinical picture.
Imaging also has its place. Thyroid ultrasound allows us to look at the structure of the gland itself. Changes in tissue texture, blood flow, or the presence of nodules may provide information that cannot be obtained through blood testing alone. Used together, laboratory findings and imaging often provide a much more complete understanding than either could achieve independently.
Testing Should Guide Questions, Not Replace Them
One of the easiest mistakes to make is believing that health can be reduced to a collection of laboratory values. Blood tests are extraordinarily useful, but they are still only measurements taken at one moment in time. They do not measure resilience, daily function, quality of sleep, emotional wellbeing, digestive comfort, or the countless ways people experience health in their everyday lives.
Over the years I have met many people whose laboratory results appeared reassuring while they continued struggling with symptoms that significantly affected their quality of life. I have also worked with others whose laboratory findings looked quite concerning, yet they remained remarkably functional because their bodies had adapted in ways that numbers alone could never fully describe.
This is one reason I believe careful listening remains one of the most valuable clinical skills. A person’s story often provides as much insight as any laboratory investigation. When that story is combined with appropriate testing, patterns begin to emerge that neither could reveal on their own.
By this point in the article we have explored how Hashimoto’s develops, why the immune system may lose tolerance, the many factors that continue influencing immune regulation, and why the symptoms can vary so greatly from one person to another. The final question becomes a practical one. If Hashimoto’s reflects changes across multiple systems rather than the thyroid alone, where do we begin supporting the body?
That is the question we will explore next.
Supporting the Terrain
By now, I hope one thing has become clear. Hashimoto’s is not simply a condition of the thyroid. The thyroid is the tissue where the immune response becomes visible, but every section of this article has pointed toward a much broader story. The digestive tract, the microbiome, the immune system, hormones, nutrient status, the nervous system, and the environment all contribute to the internal conditions in which the thyroid functions. Looking at only one part of that system makes it difficult to understand why the condition developed in the first place.
This way of thinking has changed the way I work with people.
I rarely begin by asking how to support the thyroid. Instead, I begin by asking what the body has been responding to over the months or years before the diagnosis was made. That question often leads us in a very different direction. Rather than focusing immediately on replacing what has been lost, we begin looking at the systems that have been quietly asking for support long before thyroid function began to decline.
The digestive tract is usually where I begin because it is one of the primary places where the immune system meets the outside world. Every meal, every microorganism, every nutrient, and every environmental exposure passes through this remarkable interface. Supporting digestion is not simply about improving bowel function or reducing discomfort after eating. It is about restoring one of the body’s most important communication systems.
For many people, this begins with food.
I encourage a diet built around whole, minimally processed foods that provide diversity rather than restriction. A wide variety of vegetables, herbs, roots, seasonal fruits, quality proteins, healthy fats, nuts, seeds, and traditionally prepared foods provides not only nutrients but also the fibres and plant compounds that nourish the microbiome. I often encourage people to think less about counting nutrients and more about feeding the living ecosystem within them.
When digestive symptoms are present, it may also be worthwhile to temporarily remove foods that appear to be maintaining immune activity while allowing the intestinal lining an opportunity to recover. For some people this may include gluten, while others may find that dairy or other foods are contributing to ongoing symptoms. I do not believe in permanently restricting foods without good reason, nor do I think every person with Hashimoto’s requires the same dietary approach. The body is remarkably individual, and careful observation remains one of our greatest tools.
As the digestive tract begins functioning more efficiently, it becomes much easier for the body to absorb and utilize the nutrients required for healthy immune regulation. This is one reason I rarely think of nutrition in terms of isolated supplements alone. Whole foods contain thousands of compounds that work together in ways we are only beginning to understand. Supplements certainly have their place, particularly when deficiencies have been identified, but they work best when they support an already improving foundation rather than attempting to replace one.
There are times when additional support for the digestive tract may be appropriate. Nutrients and herbs such as L-glutamine, collagen or gelatin, marshmallow root, slippery elm, quercetin, and zinc carnosine have all been studied for their ability to support the intestinal lining while it repairs. These approaches are not treating Hashimoto’s directly. They are supporting one of the body’s most important barriers, allowing the immune system to receive different information than it has been receiving.
As digestion improves, attention can then turn toward rebuilding nutritional reserves. Rather than thinking of vitamins and minerals as isolated therapies, I prefer to see them as the raw materials that every cell depends upon each day. The thyroid cannot function normally without adequate nutritional support, and neither can the immune system. Correcting deficiencies does not force the body to heal, but it removes unnecessary obstacles that may be limiting its ability to regulate itself.
Lifestyle deserves the same thoughtful attention.
Sleep is one of the body’s most important periods of repair, yet it is often sacrificed in modern life. Movement supports circulation, metabolism, lymphatic flow, muscle function, and emotional wellbeing, but it should be appropriate for the person’s current level of health rather than becoming another source of physiological stress. Time outdoors, meaningful relationships, sunlight, and opportunities for genuine rest all influence the nervous system in ways that are difficult to measure yet impossible to ignore.
One lesson I have learned over the years is that healing rarely responds well to urgency. Many people living with Hashimoto’s have spent years searching for the one diet, the one supplement, or the one treatment that will restore everything quickly. Unfortunately, the body seldom works that way. Just as the condition usually develops gradually, improvement often unfolds gradually as well. Small, consistent changes maintained over time are usually far more powerful than dramatic interventions that cannot be sustained.
People often ask whether thyroid medication still has a place within this broader approach. My answer is both yes and no. In the allopathic world, medication is often recommended quickly, sometimes without a deeper conversation about digestion, the microbiome, mineral status, stress, hormones, diet, or the immune system itself. Because people are often frightened by the diagnosis, many accept medication as the only path forward without realizing there may be more to understand and support.
When the thyroid has lost enough functional tissue, thyroid hormone replacement may become necessary. It can help restore energy, metabolism, concentration, temperature regulation, and quality of life. But this is still addressing the result of the process, not the beginning of the story.
The deeper question is why the immune system began targeting the thyroid in the first place. Medication may replace hormones the gland can no longer produce, but it does not rebuild immune tolerance, repair the digestive terrain, restore microbial diversity, correct mineral depletion, calm the nervous system, or reduce the burdens that may have contributed to the immune response. This is why I believe the cause deserves as much attention as the consequence.
Throughout this article, I have returned to the relationship between the human body and the soil because the similarities are impossible for me to ignore. Healthy soil is not created by one bacterium, one fungus, or one mineral. It emerges through the relationships between countless living organisms that communicate, recycle nutrients, build structure, regulate water, and support the whole ecosystem. When enough of those relationships are disturbed, the soil loses resilience. When those relationships are restored, the land often begins recovering in ways that once seemed impossible.
The human body follows the same principle. The microbiome, digestive tract, immune system, hormones, metabolism, nervous system, and every organ of the body exist within an intricate web of relationships. None functions alone for very long. When communication between these systems weakens, symptoms often become the visible sign that something deeper has been changing for years. The symptom is not always the problem itself. Often, it is the body’s way of drawing our attention toward relationships that have become strained.
This perspective has changed my understanding of Hashimoto’s more than anything else. I no longer see a body attacking itself without reason. I see an intelligent biological system responding to years of changing information. That information may have come from the digestive tract, the microbiome, nutrient depletion, hormonal shifts, environmental exposures, chronic stress, previous infections, or many small influences accumulating over time. Every person’s story is different, yet the same principle remains: living systems respond to the conditions in which they exist.
Not every thyroid will recover completely. Some damage may be permanent, and thyroid hormone replacement may remain an important part of long-term care for some. What I have observed, however, is that people often regain far more health than they believed possible when the focus shifts from treating the thyroid alone to understanding and supporting the entire ecosystem in which the thyroid lives.
Perhaps that is the most valuable lesson Hashimoto’s has taught me. The diagnosis is not the end of the story and should never trap people in a prison of “diagnosis”. In many ways, it can be the beginning. It invites us to become curious rather than fearful, to look beyond the thyroid itself, and to understand the remarkable relationships that sustain health every day. When we begin restoring those relationships with patience, consistency, and respect for the body’s remarkable intelligence, we often discover that healing is not about forcing the body to change. It is about creating the conditions that allow it to do what it has been trying to do all along.
