Patients with a family history of hypothyroidism often ask us questions like these: Is hypothyroidism genetic? Will I become hypothyroid if my mother and sister both have thyroid disease? If hypothyroid disease runs in my family, does that mean I’ll always struggle with my thyroid health?
Research in epigenetics does suggest that your genetics influence your risk of developing hypothyroidism. However, it’s important to emphasize that your genes aren’t the whole picture.
Studies suggest that whether or not your genetic risk expresses itself is significantly affected by how you live your life. Specifically, this means your diet, stress, and environment. This means that you can affect your health outcomes by making good choices.
In this article, we’ll explain what hypothyroidism is, the connection between epigenetics and thyroid disease, and what you can do to maintain your thyroid health and improve your hypothyroidism.
What Is Hypothyroidism?
Hypothyroidism — an underactive thyroid — is when your thyroid gland doesn’t make enough thyroid hormone.
Common symptoms of hypothyroidism include:
- Weight gain or obesity
- Dry skin
- Hair loss
- Feeling cold
- Brain fog
- Low sex drive
According to the American Thyroid Association, the most common type of hypothyroidism is autoimmune thyroiditis, also called Hashimoto’s thyroiditis. The estimated prevalence of Hashimoto’s disease is between 1% and 2% in the United States, and women are 10 times more likely to have it than men .
Autoimmune thyroiditis means that your immune system is attacking your thyroid gland, which can impair your thyroid function.
Additional thyroid symptoms associated with Hashimoto’s thyroiditis include non-painful goiter, thyroid nodules, or pain and swelling in your thyroid area.
Is Hypothyroidism Genetic?
It’s not uncommon to meet hypothyroid women whose mothers, aunts, and daughters are also hypothyroid. Is there a genetic link? In short, the answer is “yes.” Studies have found that:
- Having a first-degree family member with a thyroid disorder is an increased risk factor for developing a thyroid condition .
- Approximately 30%-60% of hypothyroidism is associated with a family history of hypothyroidism [3, 4].
Researchers use genetic sequencing tests to identify likely candidate genes that may increase the risk of thyroid problems, including both hypothyroidism and hyperthyroidism. Let’s explore what they’ve learned about genetics and specific thyroid conditions.
Hashimoto’s Thyroiditis and Genetics
Hashimoto’s disease (autoimmune hypothyroidism) is thought to be caused by a combination of inherited genes and environmental triggers [5, 6].
Four particular gene regions, including the thyroid-stimulating hormone receptor (TSHR), are associated with autoimmune thyroid disease and autoimmune disease in general [7, 8]. However, the specific genes or gene combinations that cause hypothyroidism remain unclear [9, 10], and researchers have been unable to pinpoint the exact genes responsible for Hashimoto’s .
Despite the genetic risks of developing Hashimoto’s thyroiditis, a family history of thyroid disease doesn’t sentence you to becoming hypothyroid. And if you are diagnosed with Hashimoto’s, you can still lead a healthy life. Autoimmune hypothyroidism generally responds to standard medical treatment as well as diet and lifestyle improvements.
Congenital Hypothyroidism and Genetics
A much rarer form of hypothyroidism is congenital hypothyroidism due to a physical abnormality of the thyroid gland. It can also be caused by a problem with the pituitary gland, which normally signals the thyroid to produce thyroid hormone .
Newborns are screened for congenital hypothyroidism soon after birth with a blood test, as a lack of treatment can cause severe developmental delays.
Research generally has suggested that less than 5% of congenital hypothyroidism cases are associated with known gene abnormalities . However, genetics may play a bigger role than previously thought in congenital hypothyroidism. A research team reviewing medical histories of children diagnosed with congenital hypothyroidism found that a significant portion of them had first-degree relatives with thyroid conditions , and another study found similar results .
Thyroid Disease and Epigenetics
Why are only 30-60% of hypothyroidism cases associated with family history [3, 4]? Though our genes can’t change, the field of epigenetics suggests that the way we live our lives influences whether or not those genes express themselves [5, 15].
Environmental triggers that influence thyroid genes and health include things like your iodine status , toxin exposure , or specific foods .
A common environmental trigger for thyroid disease is gut imbalance. The hygiene hypothesis suggests that Western diets and lifestyles, which are often low in exposure to and diversity of beneficial bacteria, can impact gut colonization and immune system health .
As an example of how gut bacteria can influence your thyroid health, treatment of pathogens like H. pylori  and Blastocystis hominis  have resolved thyroid conditions. SIBO (small intestinal bacterial overgrowth) has also been closely linked to thyroid disease [22, 23].
The good news is you can positively influence your thyroid health by being mindful of your food and environmental toxin exposures and by attending to your gut health.
What to Do About Hypothyroidism
Even though your genes may be part of the reason you’re hypothyroid, don’t despair about your future just yet.
For people who are truly hypothyroid, standard thyroid replacement therapy with levothyroxine (synthetic thyroid hormone) is usually quite effective. Yet many people still don’t feel well even after their thyroid labs normalize with thyroid treatment.
If this sounds like you, there are options beyond focusing on your genes, which you can’t change. Let’s talk about what you can do to improve your hypothyroidism.
Improve Your Gut Health for Better Thyroid Function
It may not seem like your gut has anything to do with your thyroid, but thyroid-like symptoms like fatigue or depression may actually come from your gut [24, 25]. Additionally, poor gut health can make it harder to absorb your thyroid medication .
Irritable bowel syndrome (IBS) , small intestinal bacterial overgrowth (SIBO) [23, 27], low stomach acid [28, 29], H. pylori infection , and leaky gut  are all associated with thyroid symptoms or thyroid disease. Treating these related conditions often improves thyroid symptoms and, in some cases, has decreased patients’ thyroid medication dose [31, 32].
Resolving gut infections  and eating a gut-healthy diet [34, 35] can help improve your thyroid symptoms and the effectiveness of your thyroid medication.
Epigenetic Eating for Hypothyroidism
What you eat and the quality of your food is important for supporting your thyroid health because epigenetic triggers, such as particular foods and iodine, are a risk for developing hypothyroidism.
For example, low-carb , gluten-free , and dairy-free diets  have been shown to influence thyroid lab markers and antibodies. Pesticides and herbicides are known to negatively impact the thyroid and other endocrine organs [17, 39, 40, 41]. And foods high in iodine or iodine supplements have been shown to heavily influence the development of hypothyroidism [42, 43, 44].
Eating organically grown food can help protect against the chemical toxins that affect your thyroid. But there are many possible healthy diets to support your thyroid health.
To choose a thyroid-supporting diet, follow these principles:
For more support in choosing the right diet for your thyroid health, reach out to our clinic or our health coach.
Many people are misdiagnosed with hypothyroidism , so it’s helpful to make sure that you have been appropriately diagnosed.
Research suggests that two common blood tests are the gold standard to diagnose hypothyroidism:
- Thyroid-stimulating hormone (TSH — also called thyrotropin)
- Free T4 (thyroxine) thyroid hormone test
You are considered hypothyroid if you have the following:
- High TSH levels
- Low T4 hormone levels
- Thyroid symptoms.
Sometimes, your doctor will also run a free T3 (triiodothyronine) thyroid hormone test. Though many functional medicine providers pay a lot of attention to the T3 hormone, research suggests that low T3 is a sign of poor gut health [46, 47]. We’ve noticed in the clinic that T3 levels typically normalize once gut health improves.
Hashimoto’s thyroiditis is diagnosed with the combination of thyroid symptoms and the following 
- Elevated TSH levels
- Low T4 levels
- Elevated levels of TPO (thyroid peroxidase) antibodies or TG (thyroglobulin) antibodies
- Changes in your thyroid gland seen on ultrasound
If you’re unsure whether your hypothyroid diagnosis is accurate, schedule a follow-up with your doctor or healthcare provider.
The Bottom Line
Though your hypothyroidism may be linked to your genes, this doesn’t mean that you are destined to — or stuck with — poor thyroid health for life. What you eat and how you live can turn those genes on or off.
This is great news. It means that you have the power to influence your thyroid health by making good choices. Improving your gut health by eating a healthy diet and treating gut infections can help make sure your thyroid genes put their best foot forward.
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