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Hyperthyroidism (Excess Thyroid Hormones)

Alternative names: Thyrotoxicosis

What is hyperthyroidism?
What are the signs of hyperthyroidism?
What causes hyperthyroidism?
How does my doctor tell if I have hyperthyroidism?
How is hyperthyroidism treated?

What is hyperthyroidism?

The thyroid gland is a butterfly-shaped organ found in the center of the neck, below the Adam's apple. It creates and stores hormones that control the body's heart rate, blood pressure, and metabolism (how the body makes energy from food). Hyperthyroidism is a condition in which the thyroid gland produces more hormones than the body needs.

What are the signs of hyperthyroidism?

Hyperthyroidism increases the body's metabolism – the rate at which you make energy from food. This can cause a person with hyperthyroidism to feel warm, and to lose weight even when eating an adequate diet. Other symptoms may include:

  • Restlessness or anxiety
  • Increased appetite
  • Rapid heart beat, or palpitations (a feeling of the heart "flopping" in the chest)
  • Changes in sex drive
  • Fatigue and/or muscle weakness
  • Frequent bowel movements
  • Double vision
  • Irregular or absent menstrual periods in female patients

What causes hyperthyroidism?

There are several different causes of hyperthyroidism. The most common is Graves' disease, which is caused by an autoimmune disorder, where the body's immune system destroys its own tissues. Other causes include:

  • Non-cancerous tumors (adenomas) of the thyroid gland
  • Tumors in the body's reproductive organs (testes or ovaries)
  • Thyroiditis, or inflammation of the thyroid gland. This is often a temporary condition.
  • Taking excessive doses of thyroid hormone
  • Taking excessive doses of iodine

How does my doctor tell if I have hyperthyroidism?

During a physical examination, your doctor may feel the enlarged thyroid in your neck. He or she may want to perform one or more of these tests to diagnose hyperthyroidism:

  • Blood tests to measure the amount of thyroid hormones and/or antibodies in your blood
  • A thyroid scan, which is an image taken of the thyroid gland after you have swallowed a small amount of radioactive iodine. Because the thyroid naturally uses iodine to produce some of its hormones, it absorbs the radioactive substance and allows the image to be made. The image will show if the thyroid gland is enlarged and overactive.

How is hyperthyroidism treated?



  • Anti-thyroid drugs may lower the production of thyroid hormones. In order to control the rapid heart rate, sweating, and anxiety caused by an overactive thyroid gland, your doctor may prescribe heart medications known as beta-blockers.


  • A doctor may use radioactive iodine to destroy part or all of the thyroid gland, and make it unable to produce thyroid hormones. The patient will need to take replacement thyroid hormones for the rest of his or her life.


  • In a subtotal thyroidectomy, a surgeon removes most of the thyroid gland. The patient will need to take replacement thyroid hormones for the rest of his or her life.
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