What is the Anterior Pituitary?

The anterior pituitary gland is the front lobe of the pituitary gland, which is found at the floor of the brain, called the sella turcica. It is also known as the adenohypophysis. There are three parts of the anterior pituitary gland: the pars distalis, which is the biggest part often producing most of the hormones; pars intermedia, which is found between the pars distalis and the posterior lobe of the pituitary gland; and the pars tuberalis, or the tubular part of the anterior pituitary gland.

The pars intermedia is a small part of the anterior pituitary gland, and produces hormones that cause the release of pigment in skin cells. This part of the gland is usually only active in children, and sometimes disappears completely by adulthood. The function of the pars tuberalis is still not completely understood, although it may be related to photoperiodism, the body's reaction to day and night.

Hormones which are secreted by the anterior pituitary gland include the growth hormones, luteinizing hormones, prolactin, adrenocorticotropic hormones, follicle stimulating hormones, and thyroid stimulating hormones. These hormones have their own particular functions. Growth hormones are important for the growth of cells and tissues inside the body. The other hormones secreted by the anterior pituitary gland act on specific target organs.

Luteinizing hormones, for instance, target the ovaries in women and the testes in men to produce important sex hormones. Prolactin, also known as luteotropic hormone, influences the mammary glands to secrete milk after the birth of a child. Follicle stimulating hormones act on the ovaries to promote the production of eggs and on the testes to promote the production of sperm. The adrenocorticotropic hormones stimulate the adrenal glands, and the thyroid stimulating hormones influence the production of thyroid hormones in the thyroid gland.

The release of these hormones is often dependent on the influence of the hypothalamus toward the anterior pituitary gland and by negative feedback from the glands which it influences. When certain hormones are needed by the body for proper functioning, the hypothalamus often detects this deficiency and sends a signal toward the pituitary gland to produce specific hormones that will, in turn, stimulate the target organ to produce the needed hormones. Negative feedback is an important process used to maintain an appropriate level of hormones as needed by the body. For example, when the hypothalamus and the anterior pituitary detect an appropriate level of thyroid hormones in the blood, it will normally stop the production of thyroid stimulating hormones, thus stopping the stimulation of the thyroid gland to produce hormones.

Tumors, infections, and other disorders affecting the hypothalamus, anterior pituitary gland, and the target organs often result to abnormalities in the secretion of hormones. Oversecretion of growth hormones at birth can result in gigantism; when it occurs in an adult, the condition results in acromegaly, which is characterized by the enlargement of some body parts and facial bones. Deficient secretion of growth hormone, on the other hand, can result in dwarfism when it occurs during childhood.