Many factors contribute to the risk of developing thyroid disease or thyroid conditions. Here is a look at some of those key risk factors.
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 6 to 8 times more likely than men to develop a thyroid condition.
Being 50 and above increases the risk of thyroid disease for both men and women.
A personal history of thyroid disease increases your current risk for 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.
A personal history of any autoimmune disease slightly increases your risk of developing an autoimmune thyroid disease such as Hashimoto's disease or Graves' disease.
A family history of thyroid disease increases your risk for developing thyroid disease. The risk is slightly greater if you have a first-degree female relative (mother, sister, daughter) with thyroid disease.
A family history of having any autoimmune disease slightly increases your risk of developing an autoimmune thyroid disease such as Hashimoto's disease or Graves' disease.
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.
The risk of developing autoimmune thyroid disease or a temporary thyroiditis increases slightly while pregnant or during the first-year postpartum.
If you are or were a smoker, you have an increased risk of developing autoimmune thyroid disease. Cigarettes contain thiocyanate, a chemical that adversely affects the thyroid gland and acts as an antithyroid agent. Researchers have found that smoking may increase the risk, severity and side effects of hypothyroidism in patients with Hashimoto's thyroiditis, and smoking worsens the effects of thyroid eye disease, a complication of Graves' disease. Smoking also reduces the effectiveness of treatment for thyroid eye disease.
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.
Lack of sufficient iodine -– iodine deficiency -– increases the risk of hypothyroidism and goiter. 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.
Medications and Treatments
Certain medical treatments and drugs increase the risk of developing an underactive thyroid. These include Interferon Beta-1b, Interleukin-4, immunosuppressants, antiretrovirals, monoclonal antibody (Campath-1H), bone marrow transplant, Lithium, and amiodarone (Cordarone), among others.
Some foods –- when eaten raw and in large quantities -- naturally contain chemicals that can promote goiter (enlarged thyroid) and cause hypothyroidism in some people. These chemicals are known as goitrogens. Some foods that are high in goitrogens include 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 is considered a goitrogen, and some studies have shown that soy may trigger or contribute to hypothyroidism, and interferes 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 overconsumping soy products, and in particular, concentrated and processed forms of soy such as those found in pills and powders.
Exposure of the neck area to radiation, such as in medical treatments for head or neck cancer, 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.
Major stress –- including major life events like death or divorce, or major physical stress like a car accident -- is considered an environmental factor for autoimmune thyroid disease.
Medical Tests Involving Radiographic Contrast Agents/Contrast Dye
Having a medical test in which an iodine-based contrast agent is used slightly increases the risk of developing a temporary thyroiditis, hypothyroidism or hyperthyroidism. (Note: Those with underlying thyroid antibodies and a tendency toward autoimmunity appear to be at more risk.)
Surgical Antiseptic Exposure
Recent exposure to a surgical antiseptic that includes iodine (such as Povidone) can increase the risk of temporary thyroiditis, hypothyroidism or hyperthyroidism. (Note: Those with underlying thyroid antibodies and a tendency toward autoimmunity appear to be at more risk.)