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7 Common Hypothyroidism Causes


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Dry skin and hair loss. Cold intolerance. Mental fog, cognitive slowing, and dementia. Weight gain. Constipation. Irregular menstruation and infertility. Painful and stiff muscles. Depression. Taken alone, any one of these symptoms would cause major problems—but for people with hypothyroidism, several of these symptoms could be present at once, making it exceedingly difficult to lead a normal, healthy life. The first step to effectively treating a thyroid disorder (and eliminating these symptoms) is understanding the root cause of your hypothyroidism.

hypothyroidism causes
Identifying the cause of your hypothyroidism is the first step to treating it. iStock/Andrey Shevchuk

Hypothyroidism is quite common, and I see it frequently in my clinical work with patients. People may seek treatment because they’re experiencing some symptoms of hypothyroidism without knowing what’s driving them, or they may have even undergone testing that showed “normal” thyroid function. It’s a frustrating situation to be in: you’re experiencing symptoms, you know something isn’t right, but your doctor hasn’t been able to identify or address the problem.

What’s causing your hypothyroidism? Check out this article for seven common causes, and find out how to treat them using the Functional Medicine approach. #functionalmedicine #wellness #chriskresser

In conventional medicine, the standard of care for thyroid disorders is often inadequate. They’re frequently undiagnosed, and when they are discovered, the typical treatment method is prescribing replacement hormones without much investigation into what’s causing the problem. A better approach would be determining the root cause of your thyroid disorder and addressing that, giving you true relief from your symptoms. In this article, I’ll go over seven common underlying causes of hypothyroidism and talk about my typical approach in addressing them. 

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What Is Hypothyroidism?

The thyroid, a small but important endocrine gland located in the base of the neck, releases hormones that are involved in the regulation of your metabolism as well as your endocrine, cardiovascular, neurological, and immune function. Every cell in your body has receptors for those hormones, and your thyroid directly acts on your: (1)

  • Cardiovascular system
  • Gastrointestinal tract
  • Bone metabolism
  • Glucose metabolism
  • Body temperature regulation
  • Red blood cell metabolism
  • Gallbladder and liver function
  • Steroid hormone production
  • Lipid and cholesterol metabolism
  • Protein metabolism

That’s why, if something isn’t working right with your thyroid, you’ll feel a diverse (and disruptive) array of symptoms throughout your body. 

Hypothyroidism occurs when the thyroid is underactive (the opposite condition, hyperthyroidism, occurs when the thyroid is overactive and producing too much thyroid hormone). The process of production, conversion, and uptake of thyroid hormones is quite complex—if any step goes wrong, symptoms of low thyroid can occur.

While I won’t go into the full production, conversion, and uptake process in this article, here’s a quick overview of some of the key players involved:

  • Thyrotropin-releasing hormone (TRH): This hormone is produced in the hypothalamus, and it signals to the pituitary gland how much thyroid-stimulating hormone (TSH) to produce.
  • TSH: Produced by the pituitary gland, TSH stimulates the thyroid to produce the thyroid hormones T4 and T3. Elevated TSH levels could indicate an underfunctioning thyroid. It’s crucial to note that not everyone with hypothyroidism will fit this pattern; low levels of TSH can also indicate a problem if coupled with low levels of thyroid hormones.
  • Thyroxine (T4) and triiodothyronine (T3): Collectively known as “thyroid hormones,” T4 and T3 are produced by the thyroid. T4, the inactive form of thyroid hormone, must be converted to T3 before the body can use it. In my work, I look at total T4 and T3 (these are bound to a protein carrier and can be circulated in the bloodstream) and free T4 and T3 (these are separated from that carrier and can bind to cell receptors and perform their function).
  • Thyroid-binding globulin (TBG): TBG is the protein carrier that binds to T4 and T3 and transports those hormones through the blood. Too much TBG can lead to lower levels of free T4 and T3.
  • Thyroid antibodies: In cases of autoimmunity, these antibodies attack and damage the thyroid gland. I look at thyroid peroxidase (TPO) antibodies (Ab) and thyroglobulin (Tg) Ab. These antibodies can show up years before clinical hypothyroidism develops, making it especially important to spot them early on.

As I mentioned with TSH, there are several patterns of hypothyroidism that don’t align with the conventional view of these markers. For more on those, check out “5 Thyroid Patterns That Won’t Show up on Standard Lab Tests.”

Why It’s Important to Understand What’s Causing Your Thyroid Disorder

In Functional Medicine, we always want to understand the root cause of a chronic illness—in fact, that’s the only way to treat it effectively. It’s not enough to simply address symptoms; often, taking a symptom-based approach to treatment leaves people stuck taking a myriad of medications, none of which address the condition that’s causing the problem in the first place. Some of those medications may even have uncomfortable side effects of their own.

This is particularly true for people with hypothyroidism. If, for example, you’re experiencing subclinical hypothyroidism (meaning your thyroid hormone levels are within what’s considered a normal range in conventional medicine) alongside symptoms like weight gain, lethargy, depression, and constipation, you may end up on medications to address each one of those problems without receiving any treatment aimed at the true cause: a thyroid disorder. What’s more, many of the issues that can cause hypothyroidism will affect more than just your thyroid. Gut dysbiosis, for example, could have an impact on your cardiovascular health, brain function, skin health, and even your risk of developing cancer. Addressing your low thyroid without improving your gut health won’t solve any of those associated issues.

Some underlying causes will also interfere with the effectiveness of the treatment itself. Inflammation, which is characteristic of autoimmunity, will cause a decrease in thyroid receptor site sensitivity. That means even substantial doses of replacement thyroid hormone won’t improve symptoms for people with autoimmunity, since their cells aren’t able to utilize it. They’ll need to address their inflammation first before any treatment can take effect, thus the importance of uncovering the root cause of the problem.

The situation above is a frustrating, albeit common, one for patients and practitioners alike. As a doctor, you want nothing more than to help your patient heal from their thyroid disorder, but without understanding the root cause, often the best option is to prescribe replacement hormones and monitor their progress. In the ADAPT Practitioner Training Program, we teach licensed practitioners how to take a Functional Medicine approach to healthcare by discovering the underlying cause of an illness and addressing it head-on. Our yearlong, virtual course goes in-depth on how to:

  • Address the root cause of chronic illnesses like hypothyroidism.
  • Adopt a holistic, patient-centered approach to your work.
  • Integrate ancestral health and nutrition concepts into your treatment plans.
  • Manage your Functional Medicine practice effectively.

That approach could spell the difference between a patient who continues to experience problems despite their thyroid medication and one who sees a total reversal in their symptoms and relief from their illness. Click here to find out how the ADAPT Practitioner Training Program can help you help your patients.

Seven Common Causes of Hypothyroidism

So what’s causing your low thyroid? Let’s explore seven of the most common reasons that hypothyroidism develops.

1. Autoimmune Thyroiditis, or Hashimoto’s Disease

Autoimmunity is, by far, the most common cause of hypothyroidism for men and women in the Western world, accounting for around 90 percent of hypothyroidism in adults. (2) Autoimmune thyroiditis, or Hashimoto’s disease, affects around five out of every 100 people in the United States (and it’s at least eight times more common in women than men). (3) In the Western world, Hashimoto’s disease is also a common cause of goiter (while in other parts of the globe, an iodine deficiency is frequently the culprit).

As with other autoimmune disorders, Hashimoto’s disease is a case of mistaken identity. The immune system misidentifies the thyroid gland as a foreign pathogen and produces thyroid antibodies to attack it, progressively destroying the thyroid tissue. (4) As you might guess, that significantly impairs the thyroid’s ability to function, leading to low levels of thyroid hormones and causing hypothyroidism.

Interestingly, there may also be a connection between Helicobacter pylori infection and Hashimoto’s disease. A particularly virulent strain of H. pylori has been found in those with Hashimoto’s disease, and treatment of the infection reduces thyroid autoantibodies. (5) This strain of H. pylori could trigger thyroid autoimmunity because it shares a very similar genetic sequence with an enzyme involved in thyroid hormone synthesis. This similarity may induce a damaging cross-reaction with thyroid tissue and subsequent autoimmunity.

2. Exposure to Environmental Toxins

The thyroid gland is quite susceptible to damage from environmental toxins and can easily accumulate heavy metals and toxins that mimic thyroid hormone structure or contain halogens. That includes:

  • Industrial chemicals: Perchlorate, polychlorinated biphenyls (PCBs), and dioxin are common industrial pollutants and have all been found to disrupt thyroid function. (6, 7, 8)
  • Pesticides and herbicides: Pesticides and herbicides can interfere with the thyroid by inhibiting thyroid hormone gene expression, impeding the thyroid’s uptake of iodine, binding to thyroid hormone transport proteins, reducing cellular uptake of thyroid hormone, and increasing thyroid hormone clearance from the body. (9, 10)
  • Toxins found in consumer goods: Flame retardants (found in computer and TV screens, furniture, carpet padding, and more), plasticizers like bisphenol A (BPA) and phthalates, triclosan (an antibacterial chemical found in hand soap), and perfluorooctanoic acid (PFOA) from non-stick cookware and stain-resistant fabrics can also harm your thyroid. (11, 12, 13, 14, 15)
  • Heavy metals: Cadmium, lead, mercury, and aluminum can impact the thyroid through a variety of mechanisms. (16, 17, 18, 19) Many of these contaminants are increasingly common in our environment due to industrialization and pollution.

Many of these toxins cause outright damage to the thyroid, while others:

  • Interfere with the production of T4 and T3
  • Reduce available thyroid receptors
  • Hamper the conversion of T4 to T3
  • Cause other problems during the production, conversion, and reuptake process

3. Blood Sugar Imbalance

Like hypothyroidism, blood sugar disorders are exceedingly common: (20, 21, 22)

  • More than 30 million Americans have diabetes.
  • More than 84 million adults in the United States have prediabetes.
  • More than 70 percent of U.S. adults are overweight or obese.
  • An estimated one in two Americans may be obese by 2030, and one in four may be “severely obese.”

These statistics are worrying on their own, but they also mean there’s a growing number of people who are at risk for thyroid disorders alongside other major health problems.

The relationship between your thyroid and blood sugar is complex. The thyroid acts on your blood sugar metabolism—so if your thyroid isn’t functioning normally, your blood sugar balance may be out of whack—but your blood sugar also acts on your thyroid. (23) If you’re experiencing metabolic syndrome, your thyroid function will probably be impacted, as well.

Research shows that insulin resistance (common in people with chronically high blood sugar) can increase the destruction of the thyroid in people with Hashimoto’s disease. (24) Low blood sugar (hypoglycemia) can also damage thyroid health by suppressing your pituitary gland’s function (and as I mentioned, the pituitary produces TSH, which spurs your thyroid on to produce T4 and T3). (25)

4. Food Intolerance

Gluten intolerance appears to be closely linked with Hashimoto’s disease. Many people who have Hashimoto’s disease also suffer from celiac disease (an autoimmune condition), and a gluten-free diet produces improvements in thyroid health. (26, 27) Why does this connection exist? The molecular structure of gliadin, which forms the protein portion of gluten, closely resembles the structure of your thyroid gland. If you’re sensitive to gluten and you consume it, your immune system will tag that gliadin for destruction—and attack your thyroid gland in the process. This is particularly problematic when you consider:

  • Celiac disease affects 1 to 5 percent of Americans, but many people don’t experience obvious symptoms and may not know they have the condition. (28, 29)
  • An immune response to gluten can last up to six months after you eat it. (30)

Goitrogenic foods can also cause issues for people with low thyroid. Goitrogens are foods that may cause swelling of the thyroid (goiter) by interfering with the gland’s iodine uptake. At low concentrations, you may be able to offset the impact of goitrogens by supplementing with iodine; but a large intake will negatively affect your thyroid. (31) A partial list of goitrogenic foods includes (for a full list of goitrogens, click here):

  • Cruciferous vegetables like broccoli, cauliflower, cabbage, and bok choy
  • The Rosaceae family of fruits, which includes cherries, peaches, raspberries, strawberries, and apricots
  • Other foods like sweet potatoes, bamboo shoots, soy, and yuca

5. Gut Dysbiosis

Your gut microbiome is connected to nearly every aspect of your health—including the health and function of your thyroid. The relationship between your gut and your thyroid is deep and complex; the health of your gut impacts your thyroid function and vice versa.

Healthy gut bacteria aid in the T4 to T3 conversion process, while gut dysbiosis may negatively affect your thyroid metabolism. (32, 33) Your gut and immune system are also closely linked—a permeable intestinal barrier or leaky gut could play a role in the development of Hashimoto’s disease. (34) Your thyroid hormones also play a protective role in your gut barrier and may help prevent gut inflammation. (35, 36)

6. Hypothalamic–Pituitary–Adrenal (HPA) Axis Dysfunction and Stress

The HPA axis (made up of the hypothalamus, pituitary gland, and adrenal glands) is the body’s central stress response system. The HPA axis coordinates the release of cortisol, a hormone that allows our bodies to respond quickly to an immediate threat. Chronic stress, however, can disrupt that process and lead to HPA axis dysfunction.

The thyroid is closely tied to the HPA axis. As I mentioned, the hypothalamus produces TRH, which spurs the pituitary to produce TSH, which signals the thyroid to produce T4 and T3. As you might guess, disruptions in the hypothalamus and/or pituitary gland can interfere with that process and impact the thyroid. (37)

Chronic stress promotes the release of inflammatory cytokines, which reduce the function of the hypothalamus and pituitary gland (and, in turn, the thyroid), inhibit the conversion of thyroid hormones, cause thyroid hormone resistance, and impact other hormones that are important for proper thyroid function. (38, 39, 40, 41, 42, 43, 44) Altered cytokine production may also be linked to autoimmunity, making HPA axis dysfunction and stress critical factors to consider if you have Hashimoto’s disease. (45)

It’s important to point out that exercising too much can also disrupt the HPA axis and potentially exacerbate hypothyroidism. Excessive, intense exercise is a stressor for your body, and it may negatively affect your thyroid health.

7. Nutrient Deficiencies

Your thyroid needs specific nutrients to function correctly; a deficiency in any of these can lead to hypothyroidism. They include:

  • Iodine: Thyroid hormone is rich in iodine, and deficiency of iodine can cause both hypothyroidism and goiter. (46) Worldwide, iodine deficiency is the most common cause of hypothyroidism. (47)
  • Zinc: Zinc is required for the synthesis of thyroid hormone, and deficiency of zinc has been shown to result in hypothyroidism. (48)
  • Selenium: Selenium is required to convert T4 to T3. A selenium deficiency exacerbates conditions caused by inadequate iodine intake. (49)

There is a unique relationship between iodine, selenium, and the thyroid. On one hand, increased iodine intake may worsen an immune attack on the thyroid, making supplemental iodine a poor choice for anyone with Hashimoto’s disease. (50) On the other hand, when iodine is taken with selenium, we don’t see the same autoimmunity flare-up. (51) It appears that by balancing iodine with selenium intake, we can avoid those negative immune effects.

Treatment Strategies for Hypothyroidism

When it comes to treating any condition, my motto has always been to use the treatment option that works and causes the least harm—or, preferably, no harm at all. In the case of hypothyroidism, that often includes implementing dietary and lifestyle changes, potentially alongside supplementation and medication. And, of course, the most effective strategies for you will depend on the cause of your thyroid disorder.

Replacement Thyroid Hormone

In my work, I’ve found that medication is often necessary to correct hypothyroidism. I typically avoid pharmaceuticals where I can, but in situations where they’re effective, they do more good than harm, and there are no non-drug alternatives with the same effect, I will opt for medication. It’s important to take the right thyroid hormone based on what’s causing your hypothyroidism and to address any other underlying issues that are contributing to the problem.

Now, thyroid medication alone won’t solve Hashimoto’s disease, gut dysbiosis, blood sugar issues, or any of the other underlying causes I’ve discussed here—and that’s where diet, lifestyle, and supplements can help.

Dietary and Lifestyle Interventions

There are several dietary changes you can make that may help your hypothyroidism, such as:

  • Going gluten-free: If you have Hashimoto’s disease, I recommend eliminating gluten from your diet. Unfortunately, there is no “safe amount” of gluten if you are sensitive to it.
  • Eating an anti-inflammatory diet: An anti-inflammatory diet can be highly beneficial for anyone with Hashimoto’s disease (and it’s also a great diet to promote a healthy gut). This diet is free from nutrient-poor foods like seed oils and refined sugar, as well as foods that can trigger an immune response like nightshades, eggs, dairy, grains, and legumes (to name a few).
  • Eating organic: Eating organic produce will help you avoid harmful toxins like pesticides and herbicides.
  • Getting enough fermentable fiber: Eating foods that are rich in fermentable fiber can improve your gut health. Try apples, citrus fruit, carrots, onions, garlic, asparagus, and green banana flour.
  • Reducing intake of goitrogenic foods and preparing them properly: Boiling and steaming can reduce a food’s goitrogenic content and, of course, reducing your intake of these foods can lessen their harm.
  • Consuming adequate dietary iodine and selenium: Eating enough iodine and selenium in your diet is a great way to avoid supplementation. Seafood and iodized salt are good sources of iodine, while Brazil nuts are an excellent source of selenium. (52)
  • Potentially avoiding a ketogenic diet: Very-low-carb diets like the keto diet may decrease thyroid function. (53) This is not always the case for everyone, so if you have compelling reasons for going keto, some experimentation may be necessary.

You can also try to implement lifestyle changes, like:

  • Managing your stress: Finding relief from chronic stress can help you alleviate any HPA axis dysfunction that’s driving your thyroid issues. Strategies like yoga, meditation, breathing exercises, and mindfulness can make a big difference.
  • Practicing good sleep habits: Sleep is a must for your overall health as well as a prerequisite for a healthy gut. Aim for around eight hours of sleep each night, settle down in a cool, dark room, and limit your exposure to artificial light.
  • Developing a sustainable exercise routine: Regular exercise is beneficial for your gut health, blood sugar metabolism, and stress management, but it’s important to strike the right balance and not overtrain.
  • Getting enough sun: Sun exposure has been shown to have a protective effect against autoimmune disease. (54)
  • Purchasing a high-quality water filter: Reverse-osmosis filters can effectively remove thyroid-damaging toxins like perchlorate, pesticides, PCBs, plastics, and a wide variety of heavy metals.
  • Limiting your use of plastics: If possible, don’t drink from or store food in plastic containers. However, if you do choose to use some plastic products, look for “BPA-free” options. Keep in mind that BPA-free products may still contain other bisphenol derivatives with potential thyroid-disrupting effects.
  • Replacing your non-stick cookware: Toss your non-stick cookware and replace it with better options like enamel or stainless steel.


Finally, supplementation may be what you need to get your thyroid health back on track (and I recommend working with a practitioner to ensure you’re getting the right balance of nutrients). You may need:

Get Help for Your Hypothyroidism

The best way to heal from hypothyroidism is by working with a Functional Medicine practitioner who’s prepared to address the root cause of your disorder. It’s crucial that you find someone who can identify what’s really causing your issue, as their treatment plan will vary depending on it. And depending on that cause, your practitioner may also recommend targeted supplementation and/or medication as well as lifestyle changes, like managing your stress levels.

This is where it helps to have a collaborative team of professionals who are all dedicated to helping you alleviate your hypothyroid symptoms or reverse the illness altogether. Your care team could include:

  • A practitioner to order blood work, prescribe treatment, and monitor your progress
  • A nutritionist to help you make changes to your diet, like removing gluten, adopting an anti-inflammatory diet, or reducing your intake of goitrogens
  • A health coach to support you as you change your habits
  • A personal trainer to make sure your fitness routine provides the exercise you need without adding stress and worsening your thyroid condition
  • A mindfulness expert to help you learn how to stay present and manage your stress levels

Now imagine getting at the root cause of your thyroid disorder while having the support of an entire team of professionals who are all focused on helping you. Sounds good, doesn’t it? I believe that this collaborative model and root-cause-based approach is what’s really needed to correct hypothyroidism. That’s why it’s the model we use at the California Center for Functional Medicine.

The California Center for Functional Medicine offers an online, membership-based health transformation program developed to address the root cause of your illness and turn your health around for good. As a member, you get access to a team of professionals and tools to help you make changes and reach your health goals. If you’re looking for help with your thyroid, I encourage you to sign up now.
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