Prolactinoma Support Group

Prolactin stimulates the breast to produce milk during pregnancy. After delivery of the baby, a mother's prolactin levels fall unless she breast feeds her infant. Each time the baby nurses, prolactin levels rise to maintain milk production.

Autopsy studies indicate that 25 percent of the U.S. population have small pituitary tumors. Forty percent of these pituitary tumors produce prolactin, but most are not considered clinically significant. Clinically significant pituitary tumors affect the health of approximately 14 out of 100,000 people.

In women, high blood levels of prolactin often cause infertility and changes in menstruation. In some women, periods may disappear altogether. In others, periods may become irregular or menstrual flow may change. Women who are not pregnant or nursing may begin producing breast milk. Some women may experience a loss of libido (interest in sex). Intercourse may become painful because of vaginal dryness.

In men, the most common symptom of prolactinoma is impotence. Because men have no reliable indicator such as menstruation to signal a problem, many men delay going to the doctor until they have headaches or eye problems caused by the enlarged pituitary pressing against nearby eye nerves. They may not recognize a gradual loss of sexual function or libido. Only after treatment do some men realize they had a problem with sexual function.

A doctor will test for prolactin blood levels in women with unexplained milk secretion (galactorrhea) or irregular menses or infertility, and in men with impaired sexual function and, in rare cases, milk secretion. If prolactin is high, a doctor will test thyroid function and ask first about other conditions and medications known to raise prolactin secretion. The doctor will also request a magnetic resonance imaging (MRI), which is the most sensitive test for detecting pituitary tumors and determining their size. MRI scans may be repeated periodically to assess tumor progression and the effects of therapy. Computed Tomography (CT scan) also gives an image of the pituitary, but it is less sensitive than the MRI.

In addition to assessing the size of the pituitary tumor, doctors also look for damage to surrounding tissues, and perform tests to assess whether production of other pituitary hormones is normal. Depending on the size of the tumor, the doctor may request an eye exam with measurement of visual fields.

The goal of treatment is to return prolactin secretion to normal, reduce tumor size, correct any visual abnormalities, and restore normal pituitary function. In the case of very large tumors, only partial achievement of this goal may be possible.

Dopamine is the chemical that normally inhibits prolactin secretion, so doctors may treat prolactinoma with bromocriptine or cabergoline, drugs that act like dopamine. This type of drug is called a dopamine agonist. These drugs shrink the tumor and return prolactin levels to normal in approximately 80 % of patients. Both have been approved by the Food and Drug Administration for the treatment of hyperprolactinemia. Bromocriptine is the only dopamine agonist approved for the treatment of infertility. Another dopamine agonist, pergolide, is available in the U.S., but is not approved for treating conditions that cause high blood levels of prolactin.

Bromocriptine is associated with side effects such as nausea and dizziness. To avoid these side effects, it is important for bromocriptine treatment to start slowly.

Bromocriptine treatment should not be interrupted without consulting a qualified endocrinologist. Prolactin levels often rise again in most people when the drug is discontinued. In some, however, prolactin levels remain normal, so the doctor may suggest reducing or discontinuing treatment every two years on a trial basis.

Cabergoline is also associated with side effects such as nausea and dizziness, but these may be less common and less severe than with bromocriptine. As with bromocriptine therapy, side effects may be avoided if treatment is started slowly. If a patient's prolactin level remains normal for 6 months, a doctor may consider stopping treatment. Cabergoline should not be interrupted without consulting a qualified endocrinologist.

Surgery should be considered if medical therapy cannot be tolerated or if it fails to reduce prolactin levels, restore normal reproduction and pituitary function, and reduce tumor size. If medical therapy is only partially successful, this therapy should continue, possibly combined with surgery or radiation treatment.

The results of surgery depend a great deal on tumor size and prolactin level as well as the skill and experience of the neurosurgeon. The higher the prolactin level, the lower the chance of normalizing serum prolactin. In the best medical centers, surgery corrects prolactin levels in 80 % of patients with a serum prolactin less than 250 ng/ml. Even in patients with large tumors that cannot be completely removed, drug therapy may be able to return serum prolactin to the normal range after surgery. Depending on the size of the tumor and how much of it is removed, studies show that 20 to 50 % will recur, usually within five years.

Because the results of surgery are so dependent on the skill and knowledge of the neurosurgeon, a patient should ask the surgeon about the number of operations he or she has performed to remove pituitary tumors, and for success and complication rates in comparison to major medical centers. The best results come from surgeons who have performed many hundreds or even thousands of such operations.