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).