Thyroid Health 101: Understanding Diseases, Risk Factors and Nutrition

A butterfly-shaped gland located at the base of your neck, the thyroid produces hormones that have effects through the entire body ranging from heartbeat and blood flow, body temperature and respiratory or breathing rates to the regulation of the metabolism, reproductive hormones and the nervous system including digestive tract motility. Because this gland and its hormones impact so many systems in the body, thyroid disease can be very disruptive to health.

National surveys from 1999 through 2018 suggest the number of adults being treated for thyroid disease has increased in the United States. Women, adults aged 60 and older, and non-Hispanic white people are more likely to be affected. While it is largely unknown what causes thyroid disease, genetics and environmental factors may play roles.

Types of Thyroid Diseases

Two main problems can occur with the thyroid gland: too much thyroid hormone (hyperthyroidism) or too little (hypothyroidism). Common symptoms of hyperthyroidism include heat intolerance, weight loss accompanied by an increased appetite, anxiety, nervousness, sleep disturbances, diarrhea or frequent bowel movements, shaky hands, muscle weakness, and even heart palpitations. Common symptoms of hypothyroidism include cold intolerance, weight gain, depression, fatigue, forgetfulness, joint and muscle pain, dry skin or hair, heavy or irregular menstrual cycles and constipation. In the U.S., hypothyroidism is estimated to be more common than hyperthyroidism.

Autoimmune Thyroid Diseases

The causes of autoimmune thyroid disease are the same as other types of autoimmune diseases and are likely multifactorial including environmental, genetic and/or health-related factors. Some nutritional risk factors that may affect thyroid health include exposure to excess iodine, or iron or selenium deficiency.

Graves’ disease is a form of hyperthyroidism, and Hashimoto’s disease is a form of hypothyroidism. These are the most common reasons for an overactive and underactive thyroid. With Graves’ disease and Hashimoto’s disease, the immune system attacks the thyroid gland, causing too much or not enough thyroid hormone to be produced, respectively.

Studies show females are 4 to 10 times more likely than males to develop Hashimoto’s disease. Graves’ disease also is more common in females. Oftentimes, autoimmune thyroid diseases are accompanied by other autoimmune disorders such as celiac disease, Sjogren’s syndrome, Type 1 diabetes, rheumatoid arthritis or lupus.

Thyroid Cancer

According to the National Cancer Institute, thyroid cancer is not among the most common cancer types; it accounted for only 2.2% of all new cancers in the U.S. in 2023. Risk factors include a family history of thyroid disease, exposure to radiation and, like most thyroid diseases, this type of cancer is more common in women. It tends to be diagnosed between the ages of 55 and 64 in both sexes.

Symptoms of thyroid cancer can include swelling in the neck or presence of a lump, hoarseness, pain or trouble with swallowing or trouble breathing. There are a few different types of thyroid cancer including medullary, papillary, follicular and anaplastic. Although treatments range from surgery to chemotherapy and radiation, one unique treatment for thyroid cancer is radioactive iodine therapy. Because the thyroid heavily utilizes iodine, radiated iodine can help destroy thyroid cells while keeping other tissues healthy.

Other Thyroid Conditions

Nodules, or lumps, in the thyroid can become overactive and produce too much thyroid hormone. This is more common in older adults, and its diagnosis may include blood tests and a biopsy, which is used to examine fluid and cells inside the nodule, or other tests. Most nodules are benign, meaning non-cancerous, and may or may not need treatment.

Goiter is another thyroid condition that causes an abnormal enlargement of the thyroid, though not necessarily thyroid dysfunction. Iodine deficiency, Graves’ disease and Hashimoto’s thyroiditis are leading causes of goiter.

Thyroiditis is inflammation of the thyroid generally caused by autoimmunity or infection, and there are several types. This condition can cause thyroid hormones to leak out of the gland and into your blood stream, causing high thyroid levels initially throughout the body. This can lead to a condition called “thyrotoxicosis,” which may be followed by an underactive thyroid and require treatment for hypothyroidism.

Diagnosing and Treating Thyroid Disease

It’s important to talk to your physician about thyroid health at routine check-ups. They may ask about your family and personal medical history, do a physical examination such as feeling your neck or asking you to swallow while touching your neck, run blood tests or even advise a biopsy for thyroid cancer diagnosis, if deemed necessary.

Medications including synthetic hormones or anti-thyroid drugs are commonly prescribed for thyroid disease. Some of these medications must be taken in specific ways at specific times, so discussing your eating schedule with your health care team is very important. Other treatments can include thyroid surgery or radioactive iodine therapy.

Nutrition and Thyroid Health

If a person with thyroid disease has other autoimmune disorders and health conditions, their nutritional status may be affected. Depending on their overall health and food intake, certain nutrients may be lacking, or higher amounts may be needed if there is a deficiency. Here are some key nutrients that can affect the thyroid gland:

Iodine 

The reason table salt is “iodized” is to help people avoid developing thyroid disease. Many people get enough iodine from foods such as milk and other dairy products, seafood (fish and shellfish) and eggs, but people who follow a vegan or vegetarian eating style may not consume enough iodine. Iodized table salt can provide iodine in your diet, but other types of salt such as Himalayan and sea salts may not contain iodine. Plus, many people consume too much sodium, especially from foods that are highly processed, so they are encouraged to use less salt. However, highly processed foods are often made with salt that is not iodized.

Some plant foods can affect how iodine and thyroid medications are absorbed, especially in individuals who do not get enough iodine. These foods are called “goitgrogens” and include cruciferous vegetables, such as broccoli, cauliflower, kale and cabbage, as well as soy and millet. Cooking vegetables can lessen this effect. Most adults in the U.S. get enough iodine, so eating a moderate amount of these foods is not a concern for many Americans. The recommended dietary allowance for adults (19 years and older) is 150 micrograms of iodine per day, but higher amounts are needed during pregnancy and lactation, 220 and 290 micrograms, respectively.

Selenium 

A trace mineral, selenium is essential, and studies have shown that being deficient may be linked to thyroid disease. Adults (19 years and older) need 55 micrograms per day (or 60 micrograms during pregnancy and 70 micrograms when breastfeeding). Brazil nuts are the richest natural source of selenium, but they can increase the risk for selenium toxicity if eaten regularly. One ounce, or six to eight Brazil nuts, contains nearly 10 times the amount of selenium that is recommended daily. Other rich sources include seafood including tuna, halibut, and shrimp; chicken; turkey; pork products; eggs; and brown rice.

Zinc 

Another essential mineral, zinc is important for thyroid health. Adults (19 years and older) need 8 and 11 milligrams per day for females and males, respectively (11 milligrams during pregnancy and 12 milligrams when breastfeeding). Oysters are the richest source of zinc with 28 milligrams per 3 ounces cooked. Other good sources include beef and pork, pumpkin seeds and lentils. Eggs and dairy products such as milk and yogurt provide zinc but in lesser amounts.

Iron 

An important mineral for many systems in the body, iron is critical for proper thyroid function. Adults 19 to 50 need 18 milligrams for females and 8 milligrams for males per day (27 milligrams during pregnancy and 9 milligrams when breastfeeding) and 8 milligrams for adults 51 and older. Iron from plants often is absorbed less than iron from animal sources. Including a source of vitamin C, such as citrus fruit, with plant-based sources of iron can help to increase absorption. Fortified breakfast cereal with 100% of the daily value for iron (check the Nutrition Facts Label) is a rich source at 18 milligrams per serving. Additionally, beans, lentils, firm tofu, oysters, beef liver, sardines and a medium baked potato are good sources of iron.

It’s important to keep your thyroid healthy by eating a variety of foods that include nutrients the thyroid needs to function. Discuss thyroid health at your annual physical exam and ask your physician if testing its function is needed. Consult a registered dietitian nutritionist in your area for personalized dietary guidance and to ensure you’re getting enough of the nutrients your thyroid needs.