What Is It?

Hyperthyroidism means having abnormally high levels of thyroid hormones. Thyroid hormones, which are produced by the thyroid gland in the lower front of the neck, regulate the body’s energy. When levels of thyroid hormones are unusually high, the body burns energy faster and many vital functions speed up.

In most cases, hyperthyroidism is caused by the thyroid gland producing too much thyroid hormone. The two most common reasons for this are:

  • Graves’ disease, an immune-system disorder that causes the thyroid to put out too much thyroid hormone. Graves’ disease typically affects young women between ages 20 and 40, although about 12 percent of patients are men. Because Graves’ disease is an inherited disorder related to genetic factors, thyroid disease tends to affect several people in the same family.
  • A benign (noncancerous) thyroid tumor that secrets increased amounts of thyroid hormones in an uncontrolled manner

Very rarely, hyperthyroidism may be caused by the pituitary gland overproducing thyroid-stimulating hormone (TSH). This hormone causes the thyroid gland to produce too much thyroid hormone.

Certain types of thyroid inflammation or viral thyroid infections can cause short-term hyperthyroidism.

In rare situations, excess thyroid hormone can come from a source outside the thyroid, including struma ovarii, an abnormal tissue growth in the ovary that secretes thyroid hormone. Symptoms of hyperthyroidism also can be caused by taking thyroid supplements when they aren’t needed.


Hyperthyroidism causes the following symptoms:

  • Nervousness
  • Insomnia
  • Dramatic emotional swings
  • Sweating
  • Tremors and shakes
  • Increased heart rate
  • Frequent bowel movements
  • Unexplained weight loss, often despite an increased appetite
  • Unusual sensitivity to warm temperatures (feeling hot all the time)
  • Muscle weakness
  • Shortness of breath and heart palpitations

In women, menstrual periods may either become less frequent or stop completely. Older people may suffer develop heart failure or the chest pain of angina.

Hyperthyroidism, especially when it is due to Graves’ disease, also may produce a swelling of tissues behind the eyes that produces a characteristic protruding, staring appearance. This condition is called exophthalmos.


Your doctor will examine you, and will feel your thyroid for signs of enlargement and for abnormal lumps. He or she also may use a stethoscope to listen for signs of abnormal blood flow in the area of your thyroid gland. In other parts of your body, your doctor will check for additional signs of hyperthyroidism, including tremors, muscle wasting, moist smooth skin, excessive sweating, weakness, protruding eyes, increased heart rate and rhythm, and other cardiac abnormalities.

If your doctor suspects that you have hyperthyroidism, he or she will order blood tests to check your levels of thyroid hormones, and other tests that can determine how well your thyroid is functioning. A special type of scan, called a scintiscan also may be done. In patients with symptoms or physical findings involving the heart, an electrocardiogram (EKG) and/or other cardiac tests probably will be needed.

Expected Duration

In people with hyperthyroidism caused certain types of thyroid inflammation or viral thyroid infections, levels of thyroid hormones usually return to normal after several months. In patients with Graves’ disease, most people require long-term treatment, although the condition occasionally goes away on its own.


Hyperthyroidism cannot be prevented.


Hyperthyroidism can be treated with anti-thyroid drug therapy, using propylthiouracil (sold as a generic drug) or methimazole (Tapazole, Thiamazole) to block the formation of thyroid hormones. Beta-blocker drugs may be added to control symptoms. The most common treatment is radioactive iodine (to produce radioactive destruction of the thyroid). Another option that is used rarely now is surgery to remove a portion of the thyroid gland in a procedure called subtotal thyroidectomy.

When To Call A Professional

Call your doctor if you have the symptoms of hyperthyroidism, including constant feelings of anxiety, tremors or shakes, trouble sleeping, abnormal sweating or unusual sensitivity to warm temperatures, abnormally frequent bowel movements, palpitations, shortness of breath, or chest pain, weight loss (in spite of a normal or increased appetite), muscle weakness, wasting or menstrual irregularities.


In people treated with 12 to 24 months of anti-thyroid drugs, up to one-half have prolonged remissions of their illness. Radioactive iodide is an effective treatment. Although 40 percent to 70 percent of patients develop hypothyroidism as a side effect within 10 years, hypothyroidism is easily treated with a single pill daily.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

  A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.