Your thyroid gland, which produces hormones that influence your metabolic rate, plays an important role in your overall health. When your thyroid produces too few hormones, it can lead to a disorder known as hypothyroidism, or underactive thyroid. Several factors may influence your risk of developing this condition, including environmental triggers, genetic predisposition, diet, and lifestyle. While research points to a hereditary component of hypothyroidism, having an associated family history does not guarantee that you will also develop the disorder.  

In this article, we’ll review thyroid function, hypothyroidism, its links to autoimmunity and genetics, as well as supportive dietary and lifestyle interventions to maintain a healthy thyroid gland.

The Thyroid Gland

The thyroid, located in the front of your neck and shaped like a butterfly, is one of many glands that make up the endocrine system — a network responsible for hormone production in the body. Hormones are chemical messengers that, when released into the bloodstream, travel to different cells in the body and influence their function.

How Thyroid Hormones Influence Your Health

The thyroid gland synthesizes and releases three hormones into your bloodstream: thyroxine (T4), triiodothyronine (T3), and calcitonin. Thyroid stimulating hormone (TSH) produced by the pituitary gland located at the base of your brain communicates to the thyroid how much T4 and T3 it needs to produce. (Source)

Thyroxine, which is converted to T3 with the help of minerals iodine and selenium, regulates your metabolism and body temperature. Calcitonin regulates your blood calcium levels and supports healthy bone development. (Source, Source)

Ideally your thyroid synthesizes, uses, and replenishes its supply of hormones continuously. But like most systems in the body, there exists a delicate balancing act, as underproduction or overproduction of thyroid hormones can lead to a variety of disorders including hypothyroidism (marked by insufficient hormone production) and hyperthyroidism (excessive hormone production). (Source)

External factors that influence the up-regulation or down-regulation of thyroid hormone production include:

• nutrient intake
• stress levels
• infection
• medication use
• heavy metal and radiation exposure
• thyroid removal due to cancer treatment
• environmental influences
• pregnancy
• family history
• other autoimmune conditions

(Source, Source, Source, Source, Source)

Hypothyroidism Overview

Hypothyroidism, resulting from an underactive thyroid, is the most common of all thyroid disorders. Roughly 5% of the population aged 12 and older have been diagnosed with hypothyroidism, and it’s estimated that another 5% remain undiagnosed. (Source)

The degree to which the diagnosis affects your life may depend on the severity of your symptoms, your family history, and to what extent your thyroid and pituitary gland hormones are underperforming.

Symptoms of Underactive Thyroid

Symptoms of hypothyroidism may differ between people based on how much the disorder has progressed. These include but are not limited to:

• weight gain
• fatigue
• low libido
• dry skin
• constipation
• brain fog
• cold hands and feet
• hair loss

(Source)

Consult Your Health Care Provider to Determine Your Care Plan

If your health care provider suspects you have hypothyroidism, they may order blood work measuring your T4 and TSH levels, or other diagnostic tests including ultrasound or a radioactive iodine uptake test. They may collect a detailed family history of thyroid disease and other associated conditions and perform a physical exam of your thyroid gland. Depending on results, your provider may prescribe you hormone replacement medication, such as synthetic thyroxine. (Source, Source)

Overt Versus Subclinical Hypothyroidism

Your health care provider may use terms like “overt” or “subclinical” to define the degree of your hypothyroidism.

If both your T4 and TSH levels are abnormal, your hypothyroidism is clinically apparent or “overt.” Overt hypothyroidism can develop during any life stage, although susceptibility increases with age. Women are up to 8 times more likely to develop overt hypothyroidism compared to men. (Source, Source, Source)

If your T4 level is normal but your TSH level is abnormal, your hypothyroidism is “subclinical.” Your thyroid is functioning less than optimally, and you have a future risk of developing overt hypothyroidism. Often, subclinical hypothyroidism doesn’t present with symptoms and treatment remains controversial. Still, the American Thyroid Association’s new evidence-based guidelines support treatment of subclinical hypothyroidism during pregnancy to prevent adverse outcomes for mother and baby. (Source, Source)

Is Hypothyroidism Genetic?

Research suggests that in addition to external risk factors, inherited genes play a role in developing certain types of hypothyroidism, notably Hashimoto’s thyroiditis and congenital hypothyroidism. More research is still needed to pinpoint all the genes that influence the development of hypothyroidism in its many forms. (Source)

Hashimoto’s Thyroiditis: Autoimmune Thyroid Disease

The most common type of hypothyroidism in the United States is Hashimoto’s thyroiditis, or autoimmune thyroid disease, which occurs when the immune system produces antibodies that attack the thyroid and destroy hormone-producing cells. The resulting chronic inflammation can impair thyroid function over time, leading to an autoimmune-mediated underactive thyroid.

If left untreated, Hashimoto’s can result in goiter (an enlarged thyroid gland), cardiovascular and mental health issues, and reproduction dysfunction. In rare cases Hashimoto’s may lead to myxedema, a serious complication characterized by severe lethargy, prolonged unconsciousness, and coma. (Source, Source, Source)

Your family history can influence your risk of developing Hashimoto’s. If you have a first-degree family member (that is, a close family member such as a parent or sibling) with the disease, your risk of developing Hashimoto’s can increase by as much as 9 times compared to the general population. Screenings of Hashimoto’s patients have also found that 46% have at least one other diagnosed relative. (Source, Source)

Hashimoto’s and Other Clustered Conditions

In adults, a Hashimoto’s diagnosis often is followed by the development of other autoimmune diseases if chronic inflammation is left untreated. In one study, which assessed over 1,000 adults and pediatric patients with Hashimoto’s, associated diseases and their progression varied based on age. In 52% of adult cases, the development of Hashimoto’s preceded other autoimmune conditions, notably pernicious anemia, rheumatoid arthritis, and lupus. On the other hand, children were more likely to be diagnosed with Hashimoto’s only after first developing celiac disease or type 1 diabetes. The trend of clustered autoimmune conditions is especially common within families, further suggesting genetic predisposition. (Source)

Congenital Hypothyroidism

Other forms of hypothyroidism have a minor genetic link, including congenital hypothyroidism, a birth defect marked by a newborn’s abnormally small or altogether missing thyroid gland. Approximately 2% of cases of congenital hypothyroidism are because of genes passed down from parents to their children. In most cases, the condition results from the mother’s insufficient intake of iodine during pregnancy. (Source)

How Diet and Lifestyle Support Thyroid Health

Healthy diet, lifestyle choices, and stress management may positively influence gene expression, which is especially important if you have a family history of thyroid disease. (Source).

Personalized Iodine Intake

Iodine — a mineral found in seafood, seaweed, dairy products, eggs, chicken, liver, and iodized table salt — is required for thyroid hormone synthesis, in which T4 is converted to T3, its active form. The recommended dietary allowance of iodine for men and women is 150 mcg per day. Inadequate iodine intake contributes to the development of hypothyroidism, although this is rarely a problem in the United States. (Source, Source)

If you have Hashimoto’s, your dietary recommendations are likely to be different from those whose hypothyroidism does not have an autoimmune component. In fact, taking in too much iodine can make Hashimoto’s worse, and you might be advised to limit the iodine in your diet.  (Source)

Vary Your Diet to Optimize Thyroid Support

Other nutrients play a key role in thyroid hormone synthesis and endocrine system support, notably iron, selenium, zinc, vitamin D, vitamin A, B vitamins, and antioxidants. Eating a variety of whole foods can help ensure adequate intake of vitamins, minerals, amino acids, and nutrients in support of optimal thyroid function. (Source, Source, Source)

Should Goitrogens Be Avoided?

Consumption of goitrogens, compounds found in certain foods including cruciferous vegetables such as broccoli, kale, and Brussels sprouts, have been the subject of controversy given their ability to bind to and block iodine from being used to synthesize thyroid hormones. Research previously suggested that long-term intake and exposure to goitrogens could lead to the development of goiter (enlarged thyroid). However, recent studies have indicated that moderate consumption of goitrogens have very little effect on general thyroid health.

If you’re concerned about your goitrogen intake, incorporating cooking techniques, such as boiling and steaming cruciferous vegetables, can reduce their goitrogenic impact by inactivating the compounds via heat. (Source, Source, Source)

How An Autoimmune Friendly Diet Supports Thyroid Health

Dietary interventions, like an anti-inflammatory and autoimmune friendly diet, have been studied for their effect on Hashimoto’s. One approach, the autoimmune protocol diet, works by removing potential allergens and food groups that may cause low-grade, chronic inflammation, while also increasing intake of anti-inflammatory foods to jumpstart healing.  

In one 2019 pilot study of middle-aged, female participants diagnosed with Hashimoto’s, introducing an AIP elimination diet positively affected quality of life outcomes. While blood tests assessing thyroid hormone levels remained unchanged, participants reported reduced symptoms normally associated with their condition. Other clinical research studying the effects of a low carbohydrate diet, a gluten free diet, and a lactose free diet on thyroid function found improved blood test results or reduced symptoms when each food group was eliminated. (Source, Source, Source, Source)

The AIP diet has also been studied for its positive effect on gut health. As poor digestion may result in less than optimal absorption of prescribed thyroid medications and nutrients critical for thyroid health, ensuring proper gastrointestinal function is equally important. Gut disorders, including irritable bowel syndrome (IBS), small-intestinal bacterial overgrowth (SIBO), infections including Heliobacter pylori, and other autoimmune conditions such as celiac disease are all commonly associated with thyroid dysfunction. While the full autoimmune protocol diet has shown significant benefit when adopted, any mindful shifts to your nutrition — including more anti-inflammatory foods and adopting an autoimmune healing diet — can provide immense relief! (Source, Source, Source)

The Bottom Line on Whether Hypothyroidism Is Genetic

While hypothyroidism has a genetic component, the effect of your family history is dependent on multiple risk factors, including the intricacies of your specific diagnosis, personal medical history, dietary and lifestyle habits, as well as environmental and biological influences.

Given the effect personalized nutrition and other holistic interventions can have on influencing gene expression, a family history of thyroid disease does not guarantee your own future diagnosis and disease outcome. If you’re considering making dietary changes or introducing more nutrient dense foods to support your thyroid health, it’s important to ensure your unique bio-individuality is being addressed by working with a knowledgeable guide, such as a Nutritional Therapy Practitioner through the WellTheory membership. We are what we eat, just as what we eat can influence our genetic code.