Pituitary gland is located at the base of the brain. It controls the secretion of other endocrine glands such as thyroid, adrenal and gonads. The activity of pituitary gland itself is controlled by hypothalamus and therefore it should be rightly called master gland. The pituitary is of the size of a pea and is differentiated in to anterior, intermediate and posterior lobes.
Functions of Pituitary Gland
The anterior lobe of the pituitary is known to secrete several hormones. Somatotropin (STH or GH) stimulates the growth of the body in general, as well as the growth of the organs. Hypo secretion (less secretion) of STH in children leads to dwarfism. The dwarfs are called midgets.
In adults, it produces symptoms similar to hypothyroidism. Persons are weak with reduced genital organs and reduced fertility. The disease is called pituitary myxoedema. Hyper secretion of STH in children causes gigantism. In adults it produces Acromegaly. The most striking feature is the presence of an elongated protruding lower jaw. A protruding forehead is also present. Some times the person develops a hump.
The adrenocorticotropic hormone (ACTH) stimulates the adrenal cortex to produce corticosteroids. The thyroptic hormone (TSH) induces the production of thyroxine by the thyroid gland. The gonadotropins act on the gonads influencing their functions. Follicles stimulating hormone (FSH), leutinizing hormone (LH) or the interstitial cell-stimulating hormone (ICSH) are all gonadotropins. These hormones are secreted by the anterior lobe of pituitary gland.
The intermediate lobe secretes melanocyte stimulating hormone (MSH) which darkens the skin of many animals such as fishes and amphibians. Humans do not produce MSH. The posterior lobe of the pituitary secretes two hormones vasopressin and oxytocin. Vasopressin or antidiuretic hormone (ADH) reduces the volume of urine by stimulating re-absorption of the water in the nephrons of the kidney, where as oxytocin contracts the smooth muscles of the uterus during child birth. It is also known as ‘Milk let down’ hormone as it helps in ejection of milk from the mammary glands.