Hyperthyroidism risk factors: who is more likely to get an overactive thyroid

What hyperthyroidism is

The thyroid is a small, butterfly-shaped gland in the front of your neck (NIDDK). Its hormones control the way the body uses energy, so they affect nearly every organ, even the way your heart beats (NIDDK). With too much thyroid hormone, many of the body's functions speed up (NIDDK).

About 1 out of 100 Americans ages 12 years and older have hyperthyroidism (NIDDK).

Who is more likely to get hyperthyroidism

Hyperthyroidism is more common in women and in people older than 60 (NIDDK) (MedlinePlus). Combining the NIDDK and MedlinePlus lists, you are more likely to have it if you (NIDDK) (MedlinePlus):

• have a family history of thyroid disease
• were pregnant or had a baby within the past 6 months
• have pernicious anemia, a condition caused by a lack of vitamin B12
• have type 1 diabetes (NIDDK lists type 1 or type 2 diabetes)
• have primary adrenal insufficiency, a hormone disorder
• get large amounts of iodine, from foods such as kelp or from medicines or supplements that contain iodine
• have had thyroid surgery or a thyroid problem such as goiter (MedlinePlus list)
• use nicotine products (NIDDK list)

What causes hyperthyroidism

Hyperthyroidism has several causes (NIDDK) (MedlinePlus):

• Graves' disease, the most common cause. It is an autoimmune disorder: the immune system attacks the thyroid and makes it produce too much hormone (NIDDK) (MedlinePlus).
• Overactive thyroid nodules, lumps in the thyroid that are common and usually not cancer, but one or more can start making too much hormone. They are found most often in older adults (NIDDK).
• Thyroiditis, inflammation of the thyroid that lets stored hormone leak into the blood. Types that can cause hyperthyroidism include subacute, postpartum (after giving birth) and painless thyroiditis (NIDDK).
• Too much iodine. Some cough syrups and medicines, including some heart medicines, and seaweed and seaweed-based supplements contain a lot of iodine (NIDDK).
• Too much thyroid hormone medicine, in people who take it for hypothyroidism (NIDDK).
• A noncancerous tumor of the pituitary gland, in rare cases (NIDDK).

If you take thyroid hormone medicine, NIDDK advises seeing your doctor at least once a year to have your levels checked, and asking about interactions when you start a new medicine (NIDDK). See hypothyroidism risk factors for the underactive side.

Symptoms to know

Symptoms vary from person to person and may include (NIDDK) (MedlinePlus):

• weight loss, even with a bigger appetite
• a rapid or irregular heartbeat
• nervousness, irritability, mood swings, trouble sleeping or fatigue
• shaky hands (tremor) or muscle weakness
• sweating or trouble tolerating heat
• frequent bowel movements or diarrhea
• an enlarged thyroid in the neck, called a goiter

Older adults may have different symptoms, such as loss of appetite or withdrawing from other people, and hyperthyroidism is sometimes mistaken for depression or dementia in this age group (NIDDK) (MedlinePlus). A diagnosis cannot be based on symptoms alone; doctors use blood tests such as TSH, T3 and T4 and sometimes imaging to confirm it and find the cause (NIDDK) (MedlinePlus).

Why treatment matters

Untreated, hyperthyroidism can cause serious health problems (NIDDK) (MedlinePlus):

• an irregular heartbeat that can lead to blood clots, stroke, heart failure and other heart problems (see atrial fibrillation risk factors)
• an eye disease called Graves' ophthalmopathy
• thinning bones and osteoporosis (see osteoporosis risk factors)
• menstrual cycle and fertility problems
• pregnancy complications such as premature birth, low birth weight, high blood pressure in pregnancy and miscarriage (MedlinePlus list)

Treatment options are medicines, radioiodine therapy and thyroid surgery, chosen based on the cause, how severe it is, your age and other conditions such as pregnancy or heart disease (NIDDK) (MedlinePlus).

Common questions

Is Graves' disease the same as hyperthyroidism?

No. Graves' disease is one cause of hyperthyroidism, the most common one (NIDDK) (MedlinePlus). Nodules, thyroiditis, too much iodine and too much thyroid medicine can also cause it.

Can pregnancy cause hyperthyroidism?

Having been pregnant within the past 6 months is on both risk lists, and postpartum thyroiditis can develop after giving birth (NIDDK) (MedlinePlus). Mild hyperthyroidism during pregnancy is usually not a problem, but severe untreated hyperthyroidism can affect both mother and baby; NIDDK advises getting it under control before becoming pregnant (NIDDK).

Which risk factors can I change?

Sex, age, family history and conditions like type 1 diabetes cannot be changed. Iodine intake is on both lists: MedlinePlus advises people with hyperthyroidism to ask their provider which foods, supplements and medicines to avoid (MedlinePlus). Nicotine use is on the NIDDK list (NIDDK); see the quit smoking check. Do not change a thyroid or other medicine dose without your clinician.

Is hyperthyroidism linked to thyroid cancer?

The nodules that cause hyperthyroidism are usually not cancer (NIDDK) (MedlinePlus). For thyroid cancer itself, see thyroid cancer risk factors.