A prolactinoma is a noncancerous pituitary tumor that produces a hormone called prolactin. This results in too much prolactin in the blood.

Prolactinoma - females; Adenoma - secreting; Prolactin-secreting adenoma of the pituitary

Prolactin is a hormone that triggers the breasts to produce milk (lactation).

Prolactinoma is the most common type of pituitary tumor (adenoma). It makes up at least 30% of all pituitary adenomas. Almost all pituitary tumors are noncancerous (benign). Prolactinoma may occur as part of an inherited condition called multiple endocrine neoplasia type 1 (MEN 1)

Prolactinomas occur most commonly in people under age 40. They are about five times more common in women than in men, but are rare in children.

At least half of all prolactinomas are very small (less than 1 cm or 3/8 of an inch in diameter). These microprolactinomas are more common in women. Many small tumors stay small and never get larger.

Larger tumors, called macroprolactinomas, are more common in men. Prolactinomas in men tend to occur at an older age and can grow to a large size before any symptoms appear.

In women:

• Abnormal milk flow from the breast in a woman who is not pregnant or nursing (galactorrhea)
• Breast tenderness
• Decreased sexual interest
• Headache
• Infertility
• Stopping of menstruation not related to menopause, or irregular menstruation
• Vision changes

In men:

• Decreased sexual interest
• Enlargement of breast tissue (gynecomastia)
• Headache
• Impotence
• Infertility
• Vision changes

Symptoms caused by pressure from a larger tumor may include:

• Headache
• Lethargy
• Nasal drainage
• Nausea and vomiting
• Problems with the sense of smell
• Vision changes
  • Double vision
  • Drooping eyelids
  • Visual field loss

Note: There may be no symptoms, especially in men.

• Cranial MRI or cranial CT scan
• Decreased testosterone levels in men
• Prolactin levels

Not everyone needs treatment for prolactinoma.

Medication is usually successful in treating prolactinoma. Surgery is done in some cases where the tumor may damage vision.

In women, treatment can improve:

• Infertility
• Irregular menstruation
• Loss of sexual interest
• Milk flow that is not due to childbirth or nursing

Men should be treated when they have:

• Decreased sexual drive
• Impotence
• Infertility

Large prolactinomas usually must be treated to prevent vision loss.

Bromocriptine and cabergoline are drugs that reduce prolactin levels in both men and women. Some people have to take these drugs for life, but some people can stop taking them, especially if their tumor has disappeared from the MRI. If you stop taking the drug, however, there is a risk that the tumor may grow and produce prolactin again, especially if it is a large tumor.

Most people respond well to these drugs. However, large prolactinomas are harder to treat. Both drugs may cause dizziness and upset stomach.

Radiotherapy is usually only used in patients with prolactinoma that continues to grow or gets worse after both medication and surgery. It may be given in the form of:

• Conventional radiation
• Gamma knife or stereotactic radiosurgery -- a type of radiation therapy that focuses high-powered x-rays on a small area in the brain.

The outlook depends on the success of medical treatment or surgery. Getting tested to check whether the tumor has returned after treatment is important.

Treatment for prolactinoma may change the levels of other hormones in the body, especially if surgery is performed.

High levels of estrogen or testosterone may be involved in the growth of a prolactinoma. Women with prolactinomas should be followed closely during pregnancy, and should discuss this tumor with their health care provider before taking birth control pills.

See your health care provider if you have any symptoms of prolactinoma.

If you have had a prolactinoma in the past, call your health care provider for a general follow-up, or if your symptoms return.

Melmed S, Kleinberg D. Pituitary masses and tumors. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 9.