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Thyroid Hormones

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Topic Overview

Thyroid hormones are made by the thyroid gland. The thyroid gland makes and releases two thyroid hormones: thyroxine (T4) and triiodothyronine (T3). Thyroid hormones affect every cell and all the organs of the body. Too much thyroid hormone speeds things up and too little thyroid hormone slows things down. They:

Control the rate at which your body burns calories (your metabolism). This affects whether you gain or lose weight.
Can slow down or speed up your heartbeat.
Can raise or lower your body temperature.
Change how fast food moves through your digestive tract.
Affect muscle strength.
Control how quickly your body replaces dying cells.

The pituitary gland and the thyroid gland work together. The pituitary gland (located near the base of the brain) makes, stores, and releases thyroid-stimulating hormone (TSH). When TSH is secreted by the pituitary gland, it causes the thyroid gland to release more T3 and T4. A high TSH level means there isn't enough thyroid hormone, and a low TSH level means there is too much.

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WebMD Medical Reference from Healthwise

Last Updated: November 04, 2011

This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.