A prolactinoma is a non-cancerous 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. It also plays a role in sexual desire.

Prolactinoma is the most common type of pituitary adenoma, making up for at least 30% of all pituitary adenomas. Prolactinomas occur most commonly in people under age 40. They are about fives times more common in women than men, but are rare in children.

The size of a prolactinoma is equal to the prolactin level. In other words, the larger the tumor, the higher the level of prolactin produced the pituitary gland.

At least half of all prolactinomas are very small (less than 1 cm or 3/8ths of an inch in diameter). These micro-prolactinomas are more common in women. Larger tumors, called macro-prolactinomas, are more common in men.

Many small tumors remain small and never get larger. Prolactinomas in men tend to occur at an older age and can grow to a large size before any symptoms appear.

In women:

• Cessation of menses not related to menopause
• Abnormal milk flow from the breast in a woman who is not pregnant or nursing (galactorrhea)
• Infertility
• Decreased sexual interest
• Headache
• Visual changes

In men:

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

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

• Prolactin levels
• Cranial MRI or cranial CT scan showing a pituitary mass
• Decreased testosterone levels in men