Disorders Affecting the Thyroid
The thyroid gland, located in the front of the neck and below the larynx (voice box), plays an important role in regulating the body's metabolism and calcium balance. The small, two-inch gland consists of two lobes, one on each side of the windpipe, connected by tissue called the isthmus.
The thyroid tissue is made up of two types of cells: follicular cells and parafollicular cells. Most of the thyroid tissue consists of the follicular cells, which secrete iodine-containing hormones called thyroxine (T4) and triiodothyronine, or T3 (both hormones secreted by the thyroid which regulate metabolism). The parafollicular cells secrete the hormone calcitonin. The thyroid needs iodine to produce the hormones. Levels of hormones secreted by the thyroid are controlled by the pituitary gland's thyroid-stimulating hormone, which, in turn, is controlled by the hypothalamus.
|Hyperthyroidism (Graves Disease) |
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