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

Prolactin is a hormone that triggers lactation or milk production.

Prolactinoma is the most common type of noncancerous pituitary tumor (adenoma), making up at least 30% of all pituitary adenomas.

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

At least half of all prolactinomas are very small (less than 1 cm or 3/8ths of an inch in diameter). These microprolactinomas are more common in women. Many small tumors remain 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
• Stopping of menstruation not related to menopause
• Decreased sexual interest
• Headache
• Infertility
• Vision changes

In men:

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

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

• Cranial MRI or cranial CT scan showing a pituitary mass
• 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 not related to childbirth or nursing

Men should be treated when they have:

• Decreased sexual drive
• Impotence
• Infertility

Large prolactinomas generally must be treated to prevent vision loss.

Bromocriptine and cabergoline are drugs that reduce prolactin levels in both men and women. They usually must be taken for life. If the drug is stopped, the tumor may grow and produce prolactin again, especially if it is a large tumor. Most people respond well to these drugs, although large prolactinomas are more difficult to treat. Both drugs may cause dizziness and upset stomach.

Using bromocriptine over time can reduce the chance of being cured by removing the tumor. Therefore, if surgery is needed, it is best to remove the tumor during the first 6 months of using this drug.

Radiotherapy with conventional radiation or gamma knife is usually reserved for patients with prolactinoma that continues or gets worse after both medication and surgery.

The outlook depends greatly on the success of medical therapy or surgery. Tests to check for recurrence of the tumor following treatment are important.

• Bleeding
• Tumor regrowth

If untreated, a growing tumor can press on the optic nerves and cause:

• Blindness
• Double vision
• Permanent vision loss

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 if the symptoms return.

Melmed S, Kleinberg D. Anterior pituitary. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR, eds. Williams Textbook of Endocrinology. Philadelphia, PA: Saunders Elsevier; 2008:chap 8.