Thyroid Gland is located in the neck. Thyroid follicles secret thryoglobulin, a storage form of thyroid hormone. Thyroid stimulating hormone (TSH) from anterior pituitary causes conversion of thyroglobulin into thyroid hormones T4 and T3. Almost all body cells are targets of thyroid hormones. Thyroid hormones increase overall metabolic rate, regulate growth and development, and influence onset of sexual maturity. Calcitonin regulates calcium. Thyroid hormones regulate metabolism, thereby affecting body temperature and weight. Thryoid hormones contian iodine, and an iodine deficiency causes the body's feedback loops to request more thyroid hormones. The thyroid gland enlarges to compensate, causing a condition called goiter.