Article title: Prolactinoma: NIDDK
Main condition: Prolactinoma
Conditions: Prolactinoma, Pituitary, Pituitary tumor
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.
The pituitary gland sits in the middle of the head in a bony box called the sella turcica. The eye nerves sit directly above the pituitary gland. Enlargement of the gland can cause local symptoms such as headaches or visual disturbances. Pituitary tumors may also impair production of one or more pituitary hormones, causing reduced pituitary function (hypopituitarism).
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.
Prescription Drugs. Prolactin secretion in the pituitary is normally suppressed by the brain chemical, dopamine. Drugs that block the effects of dopamine at the pituitary or deplete dopamine stores in the brain may cause the pituitary to secrete prolactin. These drugs include the major tranquilizers trifluoperazine (Stelazine) and haloperidol (Haldol); metoclopramide (Reglan), used to treat gastroesophageal reflux and the nausea caused by certain cancer drugs; and less often, alpha methyldopa and reserpine, used to control hypertension.
Other Pituitary Tumors. Other tumors arising in or near the pituitary--such as those that cause acromegaly or Cushing's syndrome--may block the flow of dopamine from the brain to the prolactin-secreting cells.
Hypothyroidism. Increased prolactin levels are often seen in people with hypothyroidism, and doctors routinely test people with hyperprolactinemia for hypothyroidism.
Breast Stimulation also can cause a modest increase in the amount of prolactin in the blood.
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.
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. An example of a typical approach used by an experienced endocrinologist follows:
Begin by taking a quarter of a 2.5 milligram tablet of bromocriptine with a snack at bedtime. After 3 days, increase the dose to a quarter of a tablet with breakfast and a quarter at bedtime. After 3 more days, take half a tablet twice a day, and 3 days later, one tablet at night and half with breakfast. Finally, the dose is increased to one tablet twice a day. If prolactin is still high, add half a tablet with lunch. If the medication is well tolerated, increase the dose to a full tablet. If side effects develop with a higher dose, return to the previous dosage. With time, side effects disappear while the drug continues to lower prolactin.
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. An example of a typical approach used by
an experienced endocrinologist follows:
Cabergoline should not be interrupted without consulting a qualified endocrinologist.
Surgery
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.
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 percent 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 percent will recur, usually within five years.
How do I choose a skilled neurosurgeon?
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.
A woman with a prolactinoma should discuss her plans to conceive with her physician, so she can be carefully evaluated prior to becoming pregnant. This evaluation will include a magnetic resonance imaging (MRI) scan to assess the size of the tumor and an eye examination with measurement of visual fields. As soon as a patient is pregnant, her doctor will usually advise that she stop taking bromocriptine or cabergoline, the common treatments for prolactinoma. Most endocrinologists see patients every two months throughout the pregnancy. The patient should consult her endocrinologist promptly if she develops symptoms--particularly headaches, visual changes, nausea, vomiting, excessive thirst or urination, or extreme lethargy. Bromocriptine or cabergoline treatment may be renewed and additional treatment may be required if the patient develops symptoms from growth of the tumor during pregnancy.
At one time, oral contraceptives were thought to contribute to the development of prolactinomas. However, this is no longer thought to be true. Patients with prolactinoma treated with bromocriptine or cabergoline may also take oral contraceptives. Similarly, post-menopausal estrogen replacement is safe in patients with prolactinoma treated with medical therapy or surgery.
NIH Publication No. 95-3924
February 1995
e-text posted: 20 February 1998
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