pituitary gland, small oval endocrine gland that lies at the base of the brain brain, the supervisory center of the nervous system in all vertebrates. It also serves as the site of emotions, memory, self-awareness, and thought.

Anatomy and Function

..... Click the link for more information. . It is sometimes called the master gland of the body because all the other endocrine glands depend on its secretions for stimulation (see endocrine system endocrine system (ĕn`dəkrĭn)
..... Click the link for more information. ).

Anatomy and Function

Physiologically, the pituitary is divided into two distinct lobes that arise from different embryological sources. The anterior lobe, or adenohypophysis, grows upward from the pharyngeal tissue at the roof of the mouth. An intermediate lobe also originates in the pharynx, but in humans it is greatly reduced in structure and function. The posterior lobe, or neurohypophysis, grows downward from neural tissue. It is structurally continuous with the hypothalamus hypothalamus (hī'pəthăl`əməs)
..... Click the link for more information. of the brain, to which it remains attached by the hypophyseal, or pituitary, stalk. The hypothalamus controls almost all secretions of the pituitary. The posterior lobe is controlled by nerve fibers that originate in hypothalamic neurons and the anterior lobe by substances that are transported from the hypothalamus by tiny blood vessels.

Pituitary Hormones

The tissues in the anterior lobe consist of extensive vascular areas interspersed among glandular cells that secrete at least six different hormones. It was formerly believed that a master molecule was stimulated by various enzymes to produce these hormones, but present evidence indicates that each is individually synthesized, probably by a specific type of glandular cell. Three such types of cells exist in the anterior pituitary gland: acidophils, basophils, and chromophobes. The growth hormone growth hormone or somatotropin (sōmăt'ətrō`pən)
..... Click the link for more information. , thought to be synthesized by certain acidophils, stimulates all the tissues in the body to grow by effecting protein formation.

The remaining five important hormones influence body functions by stimulating target organs. Adrenocorticotropic hormone adrenocorticotropic hormone (ədrē`nōkôr'təkōtrŏp`ĭk)
..... Click the link for more information. (ACTH) controls the secretion of steroid hormones by the adrenal cortex, which affects glucose, protein, and fat metabolism; thyrotropin thyrotropin (thī'rätrō`pĭn) or thyroid-stimulating hormone
..... Click the link for more information. controls the rate of thyroxine synthesis by the thyroid gland, which is the principal regulator of body metabolic rate; prolactin, which regulates the formation of milk after the birth of an infant; and three separate gonadotropic hormones gonadotropic hormone (gō'nădətrŏp`ĭk) or gonadotropin,
..... Click the link for more information. (follicle-stimulating hormone, luteinizing hormone, and luteotropic hormone) control the growth and reproductive activity of the gonads.

The release of each of the hormones from the anterior lobe is controlled by a specific substance secreted by nerve cells in the hypothalamus. These substances, called releasing factors, are transmitted by nerve fibers to tiny capillaries in the hypophyseal stalk. They move through blood vessels to the anterior lobe, where each releasing factor is responsible for the release of a specific pituitary hormone.

The two hormones that are produced by the posterior lobe are synthesized by nerve cells in the hypothalamus. They are transported by nerve fibers to nerve endings in the posterior lobe, where they are released. The hormones are antidiuretic hormone antidiuretic hormone (ăn'tēdīy
..... Click the link for more information. (ADH or vasopressin), which alters the permeability of the kidney tubules, permitting more water to be retained by the body; and oxytocin oxytocin (ŏksĭtō`sĭn)
..... Click the link for more information. , which aids in the release of milk from mammary glands and causes uterine contractions. The only hormone that is synthesized by the intermediate lobe is the melanocyte-stimulating hormone, which appears to control skin pigmentation.

Disorders of Pituitary Hormone Secretion

Oversecretion of the pituitary hormone human growth hormone can cause gigantism gigantism, condition in which an animal or plant is far greater than normal in size. Plants are often deliberately bred to increase their size. However, among animals, gigantism is usually the result of hereditary and glandular disturbance.
..... Click the link for more information. if it occurs before growth of the long bones is complete, or acromegaly acromegaly (ăk'rōmĕg`əlē)
..... Click the link for more information. if it begins during adulthood. Undersecretion of human growth hormone can lead to dwarfism dwarfism, condition in which an animal or plant is less than normal in size and lacks the capacity for normal growth. Dwarfism is deliberately produced and perpetuated in certain species (e.g., in breeding miniature dogs and cultivating dwarf plants).
..... Click the link for more information. if experienced during childhood, and decreased endocrine function accompanied by lethargy and loss of sexual capacity in the adult.

pituitary gland

or hypophysis

Endocrine gland lying on the underside of the brain that plays a major role in regulating the endocrine system. The anterior pituitary lobe secretes six hormones that play specific roles in stimulating production of cortisol and androgens by the adrenal cortex (corticotropin), growth of eggs and sperm (follicle-stimulating hormone), production of progesterone and testosterone (luteinizing hormone), linear growth in children and bone maintenance in adults (growth hormone), milk production (prolactin), and production of thyroid hormone (thyrotropin). The posterior lobe stores and releases two hormones, oxytocin and vasopressin, from nerve cells in specialized regions of the hypothalamus that control pituitary function. These hormones stimulate uterine contraction and milk secretion (oxytocin) and blood pressure and fluid balance (vasopressin).