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Hyperthyroidism definition and facts

  • Hyperthyroidism is a condition in which there is an excessive amount of thyroid hormones.
  • Thyroid hormones regulate the metabolism of the cells.
  • Normally, the rate of thyroid hormone production is controlled by the brain from the pituitary gland, which is in turn regulated by the hypthalamus.
  • There are many possible causes of hyperthyroidism.
  • Graves' disease, the most common cause of hyperthyroidism, can be associated with eye disease (Graves' opthalmopathy).
  • Common symptoms of hyperthyroidism include
    • restlessness,
    • agitation,
    • anxiety,
    • tremors,
    • weight loss despite an increased appetite,
    • sweating,
    • rapid heart rate,
    • intolerance to heat, and
    • frequent bowel movements.
  • Treatments for hyperthyroidism include antithyroid medications, radioactive ablation, and surgery.

What is hyperthyroidism?

Hyperthyroidism is a condition in which an overactive thyroid gland is producing an excessive amount of thyroid hormones that circulate in the blood. ("Hyper" means "over" in Greek). Thyroid hormones include thyroxine (T4) and triiodothyronine (T3), representing 99.9% and 0.1% of thyroid hormones, respectively. T3 is actually the most active thyroid hormone. Much of the T4 is converted to T3 in the bloodstream.

The thyroid itself is regulated by the pituitary gland in the brain. The pituitary is further regulated by another gland in the brain, the hypothalamus.

The hypothalamus releases a hormone called thyrotropin releasing hormone (TRH), which sends a signal to the pituitary gland to release thyroid stimulating hormone (TSH). In turn, TSH sends a signal to the thyroid to release thyroid hormones. With overactivity of any of these three glands, an excessive amount of thyroid hormones can be produced, thereby resulting in hyperthyroidism

Thyrotoxicosis is a toxic condition that is caused by an excess of thyroid hormones from any cause. Thyrotoxicosis can be caused by an excessive intake of thyroid hormone or by overproduction of thyroid hormones by the thyroid gland. Because both health-care professionals and patients often use these words interchangeably, we will take some liberty by using the term "hyperthyroidism" throughout this article.

Thyroid Gland illustration - Hyperthyroidism
Thyroid Gland illustration - Hyperthyroidism

Medically Reviewed by a Doctor on 8/1/2016


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