• Choose a category
• All
• Classic-Fiction

The anterior lobe of the pituitary produces the following six hormones:

• Growth hormone (GH), which regulates body growth and development.

• Prolactin, which stimulates female breast development and milk production.

• Thyrotropin (also called thyroid-stimulating hormone, or TSH), which stimulates the thyroid gland to secrete more thyroid hormones.

• Corticotropin (also called adrenocorticotropic hormone, or ACTH), which stimulates the outer layer of the adrenal glands to secrete corticosteroid hormones.

• Follicle-stimulating hormone (FSH), which regulates the maturation of eggs in the ovaries and sperm in the testicles.

• Luteinizing hormone (LH), which stimulates the ovaries and testicles to secrete sex hormones and is a factor in the maturation of eggs and sperm.

The intermediate lobe of the pituitary gland produces one hormone, called melanocyte-stimulating hormone (MSH), which stimulates disper-sion of cells called melanocytes in the skin and regulates their production of melanin (the pigment that gives skin, hair, and eyes their color).

The pituitary gland The pituitary is a pea-sized gland that hangs from the base of the brain. It produces hormones that regulate the activity of the other endocrine glands and control many important body processes. The pituitary has three hormone-producing sections—the anterior lobe, the intermediate lobe, and the posterior lobe.

The posterior lobe of the pituitary produces the following two hormones:

• Arginine vasopressin (AVP; also called antidiuretic hormone, or ADH), which acts on the kidneys to increase the reabsorption of water and helps regulate blood pressure.

• Oxytocin, which stimulates contractions of the uterus during childbirth and stimulates the flow of milk for breastfeeding.

The release of hormones from the anterior lobe of the pituitary gland is controlled by the hypothalamus, the area of the brain directly above the pituitary. The hypothalamus forms a link between the nervous system and the endocrine system. Because of this link, psychological factors (such as emotions) and environmental events (such as the changing of the seasons) can influence the secretion of hormones and the balance of chemicals in the body. For example, severe stress causes the pituitary to secrete corticotropin, which, in turn, stimulates the adrenal glands to secrete corticosteroid hormones, which help the body cope with the stress.

Pituitary Tumors

The pituitary gland is divided into three sections—the anterior (front) lobe, the intermediate (center) lobe, and the posterior (rear) lobe. Pituitary gland tumors usually develop in the anterior lobe. The exact cause of pituitary tumors is not known, but evidence suggests that they may result from mutations in specific genes involved in cell growth.

There are two main types of pituitary tumors—pituitary adenomas and craniopharyngiomas. Pituitary adenomas are overgrowths of cells in the pituitary gland that are usually noncancerous. Although most of these tumors are less than ½ inch in diameter, they grow in a confined space and can press on and damage surrounding nerves, blood vessels, and other tissues.

Symptoms

About half of all pituitary adenomas secrete abnormal amounts of the hormone prolactin. These tumors (called prolactinomas) may cause no symptoms, or they may cause erection problems (see page 486) in men or absence of menstrual periods or breast swelling and abnormal milk production in women. Pituitary adenomas may also secrete other hormones, leading to acromegaly (see next page), gigantism, or Cushing’s disease (see page 898).

Craniopharyngiomas do not cause overproduction of any hormones but, as they enlarge, they can press on the anterior lobe, causing hypopituitarism (see page 887), or on the posterior lobe, causing diabetes insipidus (see page 887). A craniopharyngioma can also press on the optic nerves, causing headaches, double vision, and eventually blindness.

Diagnosis

Diagnosis of a pituitary tumor is based on the symptoms and a physical