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Overview

The pituitary gland is a tiny organ, the size of a pea, found at the base of the brain. As the “master gland” of the body, it produces many hormones that travel throughout the body, directing certain processes or stimulating (causing) other glands to produce other hormones.

The pituitary gland makes or stores many different hormones. The following hormones are made in the anterior (front part) of the pituitary gland:

  • Prolactin - Prolactin stimulates breast milk production after childbirth. It also affects sex hormone levels from ovaries in women and from testes (testicles) in men, as well as fertility.
  • Growth hormone (GH) - GH stimulates growth in childhood and is important for maintaining a healthy body composition and well-being in adults. In adults, GH is important for maintaining muscle mass and bone mass. It also affects fat distribution in the body. Read about growth hormone excess
  • Adrenocorticotropin (ACTH) - ACTH stimulates the production of cortisol by the adrenal glands—small glands that sit on top of the kidneys. Cortisol, a "stress hormone," is vital to our survival. It helps maintain blood pressure and blood glucose (sugar) levels, and is produced in larger amounts when we’re under stress—especially after illness or injury. Read about having too much ACTH.
  • Thyroid-stimulating hormone (TSH) - TSH stimulates the thyroid gland to produce thyroid hormones, which regulate the body's metabolism, energy balance, growth, and nervous system activity. Read about TSH-secreting tumors.
  • Luteinizing hormone (LH) - LH stimulates testosterone production in men and egg release (ovulation) in women.
  • Follicle-stimulating hormone (FSH) - FSH promotes sperm production in men and stimulates the ovaries to produce estrogen and develop eggs in women. LH and FSH work together to enable normal function of the ovaries and testes.

The following hormones are stored in the posterior (back part) of the pituitary gland:

  • Antidiuretic hormone (ADH) - ADH, also called vasopressin, regulates water balance in the body. It conserves body water by reducing the amount of water lost in urine.
  • Oxytocin – Oxytocin causes milk to flow from the breasts in breastfeeding women, and may also help labor to progress.

Pituitary Tumors

The most frequent type of pituitary disorder is a pituitary glandtumor. These tumors are fairly common in adults. They are not brain tumors and are almost always benign (that is, not cancer). In fact, cancerous tumors of this sort are extremely rare.

There are two types of tumors—secretory and non-secretory. Secretory tumors produce too much of a hormone normally made by the pituitary, and non-secretory tumors do not. Both types of tumors can cause problems if they are large and interfere with normal function of the pituitary gland and/or nearby structures in the brain.

The problems caused by pituitary tumors fall into three general categories:

  1. Hypersecretion: Too much of any hormone in the body is caused by a secretory pituitary tumor.
  2. Hyposecretion: Too little of any hormone in the body can be caused by a large pituitary tumor, which interferes with the pituitary gland’s ability to produce hormones. Hyposecretion can also result from surgery or radiation of a tumor.
  3. Tumor mass effects: As a pituitary tumor grows and presses against the pituitary gland or other areas in the brain, it may cause headaches, vision problems, or other health effects.

Injuries, certain medications, bleeding inside or close to the pituitary, and other conditions can also affect the pituitary gland. Loss of normal pituitary function also can occur after major head trauma.

Editors:

Anne Klibanski, MD
Massachusetts General Hospital
Harvard Medical School

Nicholas Tritos, MD
Massachusetts General Hospital
Harvard Medical School

Last Review: May 2013