There are several symptoms or problems that can result from high prolactin levels. Breast enlargement or tenderness in men (called gynecomastia), or breast milk production in both men and women can occur. A high prolactin level sometimes causes infertility in a woman, or erectile dysfunction, a low testosterone level or a low sperm count in a man. If someone sees a doctor for any of these conditions, a prolactin level should be measured.
A high prolactin level may result from a pituitary tumor which is releasing too much prolactin. Pituitary tumors are actually fairly common. They are rarely cancerous, but they can cause problems either by over-producing a hormone such as prolactin, or by growing in size and pressing on surrounding structures. If a person has symptoms that lead to a diagnosis of an elevated prolactin level, an MRI of the pituitary gland is usually performed unless there is another obvious cause, such as a medication for the elevated prolactin. At other times, a person has a CT scan or MRI scan of the brain for unrelated reasons and a pituitary tumor is identified when it was not suspected. In this case a prolactin level, as well as measurement of other pituitary hormones, is usually done, even if there seem to be no symptoms. When a person has a prolactin-secreting pituitary tumor the prolactin level is usually fairly high.
Many times a person with a slightly elevated prolactin does not have a pituitary tumor on MRI scan. In this case, the tumor may be too small to be seen, or normal-appearing pituitary tissue may just be making too much prolactin. Some medications, especially those used to treat psychotic disorders such as schizophrenia, will cause the prolactin level to rise.
If the prolactin level is just a little elevated, there is no tumor and there are no symptoms, treatment may not be necessary. If a drug causing a prolactin elevation can safely be stopped, the prolactin level will fall. If there is a large pituitary tumor, or a high level causing problems, a person can be treated with bromocriptine (Parlodel) or cabergoline (Dostinex) which will usually lower the prolactin level, shrink the tumor if there is one, and lead to improvement in symptoms.