What is hyperthyroidism?

Hyperthyroidism results when the thyroid gland produces too much thyroid hormone. The thyroid is a gland located at the base of the neck below the voice box. It is about two inches long and is shaped like a butterfly. Its purpose is to produce thyroid hormones, which regulate the body's metabolism. Hyperthyroidism can speed up the body's metabolism. This condition is also referred to as "overactive thyroid."

Hyperthyroidism is a disease in which the thyroid is hyperactive and makes too much thyroid hormone. Like most conditions of the thyroid gland, it is more common in women. Hyperthyroidism can be caused by either overproduction of thyroid hormone or excessive release of thyroid hormone from the thyroid gland due to inflammation and/or destruction. It is important to distinguish between these two causes, in order to choose the appropriate treatment. A thyroid uptake scan (also known as a radioactive iodine scan) can help tell the difference between these two causes. Problems causing thyroid hormone overproduction have increased uptake on thyroid scanning (a hot scan), while thyroid gland inflammation and/or destruction have low uptake on thyroid scanning. Overproduction of thyroid hormone is the most common cause of hyperthyroidism and can be caused by Graves' disease, toxic multinodular goiter, and toxic adenoma.
Thyroid-stimulating hormone (TSH) secreting tumors cause overproduction of TSH, which stimulates the thyroid glands to make too much thyroid hormone, thyroxine, causing hyperthyroidism. This condition accelerates metabolism and can result in weight loss, rapid heartbeat and breathlessness, decreased concentration, tremor, fatigue coupled with difficulty sleeping, nervousness, heat intolerance and excessive sweating, increased bowel movements and light or absent menstrual periods.
Scott C. Makemson, MD
OBGYN (Obstetrics & Gynecology)
Hyperthyroidism is the overactivity of the thyroid gland, leading to overproduction of thyroid hormones. It can make the body's metabolism overactive, leading to symptoms such as weight loss and rapid heart rate.

Hyperthyroidism occurs when the body has too much thyroid hormone, which can be caused by an overactive thyroid that makes too much thyroid hormone or by release of thyroid hormone as the gland is destroyed.

Dr. Jack Merendino, MD
Endocrinology Diabetes & Metabolism
Hyperthyroidism is a condition in which there is too much thyroid hormone circulating in the blood stream. Symptoms include a rapid heart beat, tremor, feeling hot, frequent bowel movements or diarrhea, oily skin or hair and weight loss. A relatively common and serious complication is atrial fibrillation -- an irregular heartbeat in which the upper chambers of the heart -- the atria -- do not beat properly. Atrial fibrillation puts on at risk of stroke.

There are many causes of hyperthyroidism, and the term hyperthyroidism itself does not specify the cause. In cases of Graves’ disease or overactive thyroid nodules, the thyroid gland is making too much thyroid hormone. In Hashimoto’s thyroiditis there may be release of previously stored thyroid hormone into the bloodstream. This condition usually gives way to an underactive thyroid or a return to normal within a few weeks. Taking too much thyroid medication is also a common reason for hyperthyriodism. The symptoms of hyperthyroidism relate to the degree of hormone elevation, not the cause. Any form of hyperthyroidism can run the gamut from mild to severe.

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