Small, oval endocrine gland that lies at the base of the brain. It is called the master gland because the other endocrine glands depend on its secretions for stimulation. The pituitary has two distinct lobes, anterior and posterior. The anterior lobe secretes at least six hormones: human growth hormone, which stimulates overall body growth; ACTH(adrenocorticotropic hormone), which controls steroid hormone secretion by the adrenal cortex; thyrotropic hormone, which stimulates the activity of the thyroid gland; and three gonadotropic hormones, which
control growth and reproductive activity of the gonads (ovaries and testes). The posterior lobe secretes antidiuretic hormone, which causes water retention by the kidneys, and oxytocin, which stimulates the mammary glands to release milk and also causes uterine contractions. An overactive pituitary during childhood can cause gigantism; during adulthood, it can cause
acromegaly. Dwarfism results from pituitary deficiency in childhood. See also
Acromegaly.