The thyroid gland consists of two bodies like small walnuts; they are
connected by an isthmus beside the larynx (voice box). The thyroid gland
produces thyroid hormones T3 and T4 which
regulate the metabolism of all cells in the
body. Disorders of the thyroid gland are characterized by the inability to
produce or release sufficient thyroid hormones (hypothyroidism) or the
overactivity of the thyroid gland (hyperthyroidism).