Hyperthyroidism (Overactive Thyroid)

On this page:

• What is hyperthyroidism?
• How common is hyperthyroidism?
• Who is more likely to develop hyperthyroidism?
• Is hyperthyroidism during pregnancy a problem?
• What are the complications of hyperthyroidism?
• What are the symptoms of hyperthyroidism?
• What causes hyperthyroidism?
• How do doctors diagnose hyperthyroidism?
• How do doctors treat hyperthyroidism?
• How does eating, diet, and nutrition affect hyperthyroidism?
• Clinical Trials for Hyperthyroidism

What is hyperthyroidism?

Hyperthyroidism, also called overactive thyroid, is when the thyroid gland makes more thyroid hormones than your body needs. The thyroid is a small, butterfly-shaped gland in the front of your neck. Thyroid hormones control the way the body uses energy, so they affect nearly every organ in your body, even the way your heart beats. With too much thyroid hormone, many of your body’s functions speed up.

The thyroid is a small gland in your neck that makes thyroid hormones.

How common is hyperthyroidism?

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

Who is more likely to develop hyperthyroidism?

Hyperthyroidism is more common in women and people older than 60.² You are more likely to have hyperthyroidism if you

• have a family history of thyroid disease
• have other health problems, including
  • pernicious anemia, a condition caused by a vitamin B12 deficiency
  • type 1 or type 2 diabetes
  • primary adrenal insufficiency, a disorder of hormones
• eat large amounts of food containing iodine, such as kelp
• use medicines that contain iodine
• use nicotine products³
• were pregnant within the past 6 months

Is hyperthyroidism during pregnancy a problem?

Mild hyperthyroidism during pregnancy is usually not a problem. But severe hyperthyroidism during pregnancy, when untreated, can affect both the mother and the baby. If you have hyperthyroidism and plan to get pregnant or become pregnant, work with your doctor to get the disease under control.

Be sure your hyperthyroidism is under control before becoming pregnant.

What are the complications of hyperthyroidism?

Untreated, hyperthyroidism can cause serious health problems, including

• an irregular heartbeat that can lead to blood clots, stroke, heart failure, and other heart-related problems
• an eye disease called Graves’ ophthalmopathy
• thinning bones, osteoporosis, and muscle problems
• menstrual cycle and fertility issues

What are the symptoms of hyperthyroidism?

Symptoms of hyperthyroidism can vary from person to person and may include⁴

• weight loss despite an increased appetite
• rapid or irregular heartbeat
• nervousness, irritability, trouble sleeping, fatigue
• shaky hands, muscle weakness
• sweating or trouble tolerating heat
• frequent bowel movements 
• an enlargement in the neck, called a goiter

In older adults, hyperthyroidism is sometimes mistaken for depression or dementia. Older adults may have different symptoms, such as loss of appetite or withdrawal from people, than younger adults with hyperthyroidism. You may want to ask your doctor about hyperthyroidism if you or your loved one shows these symptoms.

What causes hyperthyroidism?

Hyperthyroidism has several causes, including

• Graves’ disease
• overactive thyroid nodules
• inflammation of the thyroid gland, called thyroiditis
• too much iodine
• too much thyroid hormone medicine
• a noncancerous tumor of the pituitary gland

Graves’ disease

Graves’ disease, the most common cause of hyperthyroidism, is an autoimmune disorder. With this disease, your immune system attacks the thyroid and causes it to make too much thyroid hormone.

Overactive thyroid nodules

Overactive thyroid nodules, or lumps in your thyroid, are common and usually not cancerous. However, one or more nodules may become overactive and produce too much thyroid hormone. Overactive nodules are found most often in older adults.

Thyroiditis

Thyroiditis is inflammation of your thyroid gland. Some types of thyroiditis can cause thyroid hormone to leak out of your thyroid gland into your bloodstream. As a result, you may develop symptoms of hyperthyroidism.

The types of thyroiditis that can cause hyperthyroidism include

• subacute thyroiditis, which involves a painfully inflamed and enlarged thyroid.
• postpartum thyroiditis, which can develop after a woman gives birth.
• painless thyroiditis, which is similar to postpartum thyroiditis, but occurs in the absence of pregnancy. Your thyroid may be enlarged. Experts think painless thyroiditis is probably an autoimmune condition.

Thyroiditis can also cause symptoms of hypothyroidism, or underactive thyroid. In some cases, after your thyroid is overactive for a period of time, it may become underactive.

Too much iodine

Your thyroid uses iodine to make thyroid hormone. How much iodine you consume affects how much thyroid hormone your thyroid makes. In some people, consuming large amounts of iodine may cause the thyroid to make too much thyroid hormone.

Some cough syrups and medicines, including some heart medicines, may contain a lot of iodine. Seaweed and seaweed-based supplements also contain a lot of iodine.

Too much thyroid hormone medicine

Some people who take thyroid hormone medicine for hypothyroidism may take too much. If you take thyroid hormone medicine, see your doctor at least once a year to have your thyroid hormone levels checked. You may need to adjust your dose if your doctor finds your thyroid hormone level is too high.

Some other medicines may also interact with thyroid hormone medicine and raise hormone levels. If you take thyroid hormone medicine, ask your doctor about interactions when starting new medicines.

Noncancerous tumor

In some rare cases, a noncancerous tumor of the pituitary gland, located at the base of the brain, can cause hyperthyroidism.

How do doctors diagnose hyperthyroidism?

A blood test might confirm a diagnosis of hyperthyroidism.

Your doctor will take a medical history and perform a physical exam. A hyperthyroidism diagnosis can’t be based on symptoms alone because many of its symptoms are the same as those of other diseases. That’s why your doctor may use several thyroid blood tests and imaging tests to confirm the diagnosis and find its cause.

Because hyperthyroidism can cause fertility problems, women who have trouble getting pregnant often get tested for thyroid problems.

How do doctors treat hyperthyroidism?

Your doctor will treat your hyperthyroidism to bring your thyroid hormone levels back to normal. Treating the disease will prevent long-term health problems, and it will relieve uncomfortable symptoms. No single treatment works for everyone.

Your treatment depends on what’s causing your hyperthyroidism and how severe it is. When recommending a treatment, your doctor will consider

• your age
• possible allergies to or side effects of the medicines
• other conditions, such as pregnancy or heart disease
• whether you have access to an experienced thyroid surgeon

Treatment options

Hyperthyroidism is usually treated with medicines, radioiodine therapy, or thyroid surgery.

This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. NIDDK translates and disseminates research findings to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by NIDDK is carefully reviewed by NIDDK scientists and other experts.

The NIDDK would like to thank:
Thanh D. Hoang, D.O., FACP, FACE, CAPTAIN (select), Walter Reed National Military Medical Center