Prolactinomas are benign tumors of the pituitary gland that secrete prolactin. This hormone is best known for inducing milk production in women, but it also serves as a regulator of sexual function in men.

Prolactinomas are the most common pituitary tumors. Men and women are equally likely to be affected. However, smaller tumors (microadenomas) are more common in women, probably because of earlier detection.

Prolactinomas may occur alone or as part of multiple endocrine tumor syndromes.

Symptoms in men include decreased sex drive, impotence, headache, visual impairment, galactorrhea (secretion of milk, which is uncommon), and symptoms of hypopituitarism (low levels of pituitary function, which result in lowered levels of thyroid or adrenal hormones).

Sexual dysfunction may result from hyperprolactinemia alone or from secondary hypogonadism (low testosterone levels).

Signs may include visual field defects, gynecomastia (enlarged breasts), galactorrhea, loss of musculature or body hair, and signs of hypothyroidism or hypoadrenalism.

Tests may show:

• Elevated prolactin
• Low testosterone
• Low FSH and LH
• MRI or CT scan showing pituitary tumor
• Abnormal visual fields

Treatment often includes use of dopamine-agonist medications (bromocriptine or cabergoline), which lower levels of prolactin. In severe cases (very large or unresponsive tumors), surgery or radiation may be necessary.

Most prolactinomas respond well to medication. However, permanent visual loss or hypopituitarism (lowered function of the pituitary gland) may occur.

Complications include visual loss and infertility. Some people experience nasal congestion, dizziness with standing, nausea, and fatigue, which may be side effects of dopamine-agonist medications.

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