Overview of the Risk Factors for Thyroid Disease

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It's a good idea to know the risk factors behind thyroid disease. This is because whether your thyroid is overactive or underactive, the initial symptoms can be quite subtle. For example, you may note that you are a little more tired or have experienced weight gain, and dismiss this as being due to age, or being less active. In other words, the symptoms are often very "nonspecific" and easily attributed to something else.

In fact, people often note, in retrospect, that they have been enduring symptoms of thyroid disease for many months or even years prior to their diagnosis. 

Let's take a look at some of the main risk factors for thyroid disease. While some of these are different for hyperthyroidism than hypothyroidism, it's important to note that a history of hyperthyroidism can lead to hypothyroidism in the future.

Gender

Women face a greater risk of developing thyroid disease than men. While experts vary in their estimates, it's said that women are anywhere from five to eight times more likely to develop a thyroid condition than men. 

Personal History

A personal history of thyroid disease increases your current risk of developing thyroid disease. For example, if after a pregnancy you had postpartum thyroiditis that resolved itself, you are at increased risk of developing a thyroid problem again after pregnancy or later in life.

In addition, a personal history of any autoimmune disease (such as lupus, type 1 diabetes, rheumatoid arthritis, pernicious anemia or Celiac disease) may increase your risk of developing an autoimmune thyroid disease such as Hashimoto's thyroiditis.

Family History

A family history of thyroid disease increases your risk of developing thyroid disease. The risk is slightly greater if you have a first-degree female relative (mother, sister, daughter) with thyroid disease.

Thyroid Surgery

Surgical removal of all or part of the thyroid usually results in hypothyroidism, an underactive thyroid.

Radioactive Iodine Treatment (RAI)

Radioactive iodine treatment to the thyroid, which is used to treat Graves' disease/hyperthyroidism, and is often used as part of thyroid cancer treatment after surgery, typically results in hypothyroidism.

Radiation Exposure

Exposure of the neck area to radiation, such as in medical treatments for head or neck cancer or Hodgkin's lymphoma, increases the risk of autoimmune thyroid disease, and thyroid cancer. Accidental radiation exposure in the environment, like that experienced by people who were exposed to radiation-contaminated air, food, milk, and water after the 1986 Chernobyl nuclear accident, also increases the risk of autoimmune thyroid disease and thyroid cancer.

Pregnancy/Post-Partum Period

The risk of developing autoimmune thyroid disease or a temporary thyroiditis increases slightly while pregnant and during the first-year postpartum. In fact, roughly 5 percent of women who give birth develop postpartum thyroiditis, but this may go undiagnosed as symptoms such as fatigue, mood swings, and hair loss are common in the postpartum period.

Cigarette Smoking

Researchers have found that smoking is linked to the development of Graves disease, especially thyroid eye disease, a complication of Grave's disease. Smoking also reduces the effectiveness of treatment for thyroid eye disease.

Iodine Deficiency and Where You Live

Lack of sufficient iodine (called iodine deficiency) increases the risk of hypothyroidism and goiter (thyroid enlargement.) Iodine deficiency is more common in developing nations and countries where table salt is not iodized.

In the U.S., iodine deficiency is seen mainly in people who restrict their salt intake, and in some people who live in areas (usually mountainous or inland) where there are lower iodine levels in soils and foods. Some people have become iodine deficient after switching to sea salt (in an attempt to eat a "healthier" diet) which does not contain iodine.

Iodine Excess (Exposure/Intake)

Use of iodine or herbal supplements containing iodine, in pill or liquid form, by people who are iodine sufficient increases the risk of autoimmune thyroid disease and hypothyroidism, and, less commonly, hyperthyroidism or thyrotoxicosis. 

Medications and Treatments

Certain medical treatments and drugs increase the risk of developing an underactive thyroid. Examples include interferon-alpha, interleukin-2, and amiodarone, among others.

Lithium can affect the thyroid gland in several ways. This medication used for bipolar disorder is linked to goiter, autoimmune thyroiditis, and hyperthyroidism.

Goitrogenic Foods

Some foods (when eaten raw and in large quantities) naturally contain chemicals that can promote goiter and cause hypothyroidism in some people. These chemicals are known as goitrogens.

Some foods that are high in goitrogens include cruciferous vegetables such as cabbage, Brussels sprouts, broccoli, turnips, rutabagas, kohlrabi, radishes, cauliflower, African cassava, millet, and kale. (Note: Those with underlying thyroid antibodies and a tendency toward autoimmunity appear to be at more risk.)

Soy Foods

Soy is considered a goitrogen, and some studies have shown that soy may trigger or contribute to hypothyroidism. It may also interfere with thyroid medication absorption. Other research is conflicting, however, and there is no consensus.

Many experts recommend that people with autoimmune thyroid disease or goiter who have not had their thyroid surgically removed avoid overconsumption of soy products, and in particular, concentrated and processed forms of soy such as those found in pills and powders. 

Other Possible Risk Factors

Other less common, but potential risk factors, include:

  • Having diseases that can infiltrate and deposit substances in the thyroid (for example, sarcoidosis or hemochromatosis) 
  • Experiencing major stress, including physical stress, like a car accident 
  • Being born with an underactive thyroid (called congenital hypothyroidism) or a thyroid gland that is in the wrong place (called ectopic hypothyroidism)

A Word From Verywell

The big picture here is that while thyroid disease is common, there are some people who are more likely to develop a thyroid condition than others. 

Even so, it's important to keep in mind that just because you have one or more risk factors does not mean you will necessarily develop thyroid disease. Likewise, you can still develop thyroid problems with zero risk factors. 

All in all, it's a statistical game—risk factors increase your chances, but they do not predict any one person's precise likelihood of having a disease.

In the end, continue to remain an advocate for your thyroid and overall health. Know your risk factors, know the symptoms of thyroid conditions, and talk to your doctor if you simply aren't feeling right.

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