Thyroxine is a complex organic compound containing iodine. Thyroxine concentration in the body is kept to the required levels through a negative feedback mechanism. The production of thyroid stimulating hormone is regulated by thyroxine. An increase in thyroxine inhibits the pituitary gland which responds by secreting less thyrotropic hormone. This in turn reduces the activity of thyroid gland leading to a drop in thyroxine production. A low thyroxine level removes the inhibitory influence on the pituitary so that more thyroid stimulating hormone is produced.
