The pituitary is a small gland (about the size of a kidney bean) located at the base of the brain, just beneath the optic (eye) nerve in a bony area called the sella turcica. It is made up of the anterior (adenohypophysis) and posterior (neurohypophysis) pituitary gland. It is often called the “master gland” because it produces a number of hormones that regulate other hormone glands in the body. The pituitary is, in turn, regulated by the hypothalamus; a portion of the brain that responds to a variety of nerve and hormonal signals from the environment and the rest of the body.
Anterior pituitary hormones include TSH (thyroid gland), ACTH (adrenal gland), GH (growth hormone), LH and FSH (reproduction) and prolactin (lactation for breast feeding). Posterior pituitary hormones include AHD (water and salt balance) and oxytocin (childbirth).
Pituitary disorders can be due to either too much, or too little pituitary hormone secretion. These disorders can result in a wide variety of different clinical conditions, depending on which hormone signal(s) are disrupted. See below for specific information about different pituitary disorders.
Prolactin is a hormone produced in the anterior pituitary gland, which normally stimulates milk production (lactation) for breastfeeding in women. The pituitary cells that produce prolactin (lactotrophs) are sensitive to a variety of stimulating factors, which can result in temporary, mild elevations of prolactin in the blood, which are not associated with any problems. However, higher prolactin levels, if sustained, can cause disruption of reproductive hormone signals, resulting in low reproductive hormones (estrogen in women, testosterone in men), as well as unwanted lactation.
Significantly elevated prolactin levels can be caused by certain medications, or by a prolactin-secreting pituitary tumors (prolactinoma). To determine the cause of high prolactin levels requires specialized testing under the guidance of a pituitary specialist (usually an endocrinologist). If a prolactinoma is discovered, it usually requires treatment with medication to reduce the prolactin level and shrink the tumor. If a tumor is very large, it can press against the optic (eye) nerve, which can affect vision. Pituitary surgery is usually not needed for most people with prolactinomas, unless the tumor is large and causing significant problems (e.g. changes in vision).
Cushing's disease is a rare condition caused by an overproduction of the adrenal hormone cortisol. The most common form of Cushing's disease is due to an excess secretion of the pituitary hormone, ACTH (adrenocorticotropic hormone), which circulates in the blood and stimulates the adrenal gland. Too much cortisol in the blood can result in a variety of symptoms, including weight gain (especially in the abdominal area), high blood pressure, thinning of the skin, easy bruising and others. These signs and symptoms are usually slow to progress and may be intermittent. For this reason, Cushing's disease is often difficult to diagnose.
The diagnosis of Cushing's disease requires specialized testing, usually by an endocrinologist. If it is determined to be due to oversecretion from the pituitary gland, then pituitary surgery is often needed. Surgery may be curative, but recurrence of Cushing's disease after pituitary surgery is relatively common. For this reason, medication is also often used.
Acromegaly is a rare condition caused by excessive growth hormone from a tumor in the pituitary gland. In children, this can result in increased height (gigantism). In adults, excessive growth hormone causes overgrowth of tissues and certain bones of the body over many years. This condition is often complicated by metabolic, heart and bone problems, including diabetes, high blood pressure, heart function problems, arthritis and carpal tunnel syndrome.
Growth hormone secreting pituitary tumors are usually treated (and in some cases cured) by surgical removal of the tumor from the pituitary gland. If the tumor cannot be completely removed, medication may also be used to control the tumor and reduce the symptoms. Anyone with acromegaly should be treated under the care of an endocrinologist.
Pituitary masses include any space-occupying lesion (mass) involving the pituitary gland. Such masses may be small or large and may produce a hormone or may not. They are almost never cancerous and do not spread to the rest of the body. Small masses (less than 1 cm) that do not produce excess hormone often do not cause problems and may never be discovered. Large masses (greater than 1 cm) can cause problems in the pituitary by compressing surrounding tissue, eroding into bone, or producing excess hormone. Pituitary masses of any size that produce excess hormone can cause significant complications depending on the hormone involved (see individual hormone conditions in other sections).
Investigation of pituitary masses requires specialized pituitary testing (usually by an endocrinologist or pituitary surgeon). Treatment of large pituitary masses often requires pituitary surgery. In cases where the mass cannot be completely removed by surgery, pituitary radiation treatments are sometimes needed to reduce the size of the tumor.
Hypopituitarism refers to low pituitary hormone secretion, involving one or more pituitary hormones. Causes of hypopituitarism include pituitary surgery, radiation treatments, large pituitary tumors, bleeding or loss of blood supply to the pituitary gland or other conditions. Symptoms of hypopituitarism are usually non-specific, including weakness, fatigue, and dizziness. In the case of sudden hypopituitarism, such as bleeding or loss of blood supply to the pituitary gland, people can experience severe headache or even loss of consciousness.
Treatment of hypopituitarism depends upon the underlying cause. Sometimes pituitary hormone secretion can recover after treatment (e.g. removal of a pituitary tumor), but often pituitary function is permanently reduced and requires long-term hormone replacement. The specific type of pituitary hormone replacement depends upon the hormones that are disrupted and may include thyroid hormone, cortisol-like hormones (e.g. hydrocortisone, or prednisone), reproductive hormones (estrogen for women and testosterone for men) and sometimes growth hormone. The decision about the proper hormone replacement should be made in conjunction with an endocrinologist.
For more information about pituitary disease, please see the links to the Canadian Society of Endocrinology & Metabolism or the Endocrine Society in the Endocrine Links section.