Hyperthyroidism is a disorder caused by excessive secretion of thyroid hormone by the thyroid, a gland in the neck that regulates body growth and metabolism. Normally, the pituitary gland, located at the base of the brain, produces a hormone (thyroid-stimulating hormone or TSH) that regulates the thyroid gland’s output of thyroid hormone.

Most often, hyperthyroidism is due to autonomous (unregulated by TSH) overproduction of thyroid hormone by an enlarged gland (Graves’ disease). This is an autoimmune disorder.

Less commonly, hyperthyroidism is caused by the growth of a single thyroid nodule that produces abnormally high amounts of thyroid hormone. Excess thyroid hormone speeds up all metabolic activity in the body (including the rate at which calories are burned) and may result in a myriad of symptoms; some can be mistaken as the result of stress or anxiety.

While hyperthyroidism is eminently treatable, severe cases can be fatal if not adequately controlled. The disorder most commonly affects those between 30 and 40 years of age and is five times more frequent in women than in men.

What Causes Hyperthyroidism?

  • Graves’ disease is an autoimmune disorder, wherein an abnormal antibody is produced that stimulates a constant production of thyroid hormone.
  • Hyperthyroidism and other thyroid disorders run in families, although the exact genetic mechanisms are unknown.
  • An excessive amount of iodine in the diet and, possibly, emotional stress may trigger the disorder in those predisposed to it.

Symptoms of Hyperthyroidism

  • Weight loss despite an increase in appetite and food consumption
  • Nervousness, anxiety, restlessness, and insomnia
  • Rapid heartbeat or palpitations
  • Tremors in the fingers or tongue
  • Increased sweating and intolerance to heat; insensitivity to cold
  • Bulging, watery eyes that feel gritty; an increased sensitivity to light
  • Swelling in the neck (goiter)
  • Fatigue and muscle weakness
  • Increased frequency of bowel movements or diarrhea
  • Unusually light or absent menstrual periods
  • Weight loss
  • An enlarged thyroid gland, which can appear as a swelling at the base of the neck

Hyperthyroidism Prevention

  • There is no way to prevent hyperthyroidism.

Hyperthyroidism Diagnosis

  • Patient history and physical exam often point to the correct diagnosis. Indicators of hyperthyroidism include elevated heart rate, nervousness, tremor, sweating, appearance of goiter, and bulging eyes.
  • Thyroid-stimulating hormone (TSH) test can detect even tiny amounts of TSH in the blood and it can also detect mild hyperthyroidism.
  • Thyroid-stimulating immunoglobulin (TSI) test may be performed to measure the level of TSI in blood.
  • Blood tests show high levels of thyroid hormones and low levels of TSH.
  • A thyroid scan is taken following the administration of radioactive iodine to determine the cause of hyperthyroidism.

How Hyperthyroidism Is Treated

  • Orally administered radioactive iodine is now the preferred method of treatment. As the thyroid absorbs the iodine, radiation destroys parts of the gland, so that it produces less thyroid hormone.
  • Propylthiouracil or methimazole, two drugs that inhibit production of thyroid hormone, may be prescribed. Although symptoms often subside within several weeks, drug therapy must usually be continued for at least a year.
  • Surgery to remove a large portion of the thyroid may be recommended for some patients with extreme thyroid enlargement.
  • Hyperthyroid patients will require frequent medical supervision throughout their lives. One risk of radioactive iodine treatment or surgery is that the thyroid will end up producing too little thyroid hormone (hypothyroidism), which then requires lifelong supplemental therapy with thyroid hormone.
  • Beta blockers may be prescribed by your physician to slow your heart rate and reduce palpitations, shaking and nervousness until your thyroid levels become normal.

When to Call a Doctor

  • Contact your doctor if you experience the symptoms of hyperthyroidism.


Johns Hopkins Symptoms and Remedies: The Complete Home Medical Reference

Simeon Margolis, M.D., Ph.D., Medical Editor

Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50

Updated by Remedy Health Media

Publication Review By: the Editorial Staff at Healthcommunities.com

Published: 07 Oct 2011

Last Modified: 19 Feb 2015