Thyroid gland

One of the main endocrine glands, which helps to regulate the rate of all the body’s internal processes. The thyroid gland is situated in the front of the neck, just below the larynx (voice box). It consists of 2 lobes, one on each side of the trachea (windpipe), joined by a portion of tissue called the isthmus. Thyroid tissue is composed of follicular cells, which secrete the iodine-containing hormones thyroxine (T) and triiodothyronine (T), and parafollicular cells (or C cells), which secrete the hormone calcitonin. T and T are important in controlling the body’s metabolism. Calcitonin helps to regulate calcium balance in the body. (See also thyroid gland, disorders of; thyroid hormones.)


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