Prolactinoma National Endocrine and Metabolic Diseases Information Service What is a prolactinoma? A prolactinoma is a benign—noncancerous— tumor of the pituitary gland that produces a hormone called prolactin. Prolactinomas are U.S. Department of Health and the most common type of pituitary tumor. Human Services Symptoms of prolactinoma are caused by hyperprolactinemia—too much prolactin in NATIONAL the blood—or by pressure of the tumor on INSTITUTES OF HEALTH surrounding tissues. Prolactin stimulates the breast to produce milk during pregnancy. After giving birth, Sella a mother’s prolactin levels fall unless she turcica breastfeeds her infant. Each time the baby nurses, prolactin levels rise to maintain milk production. Pituitary What is the pituitary gland? The pituitary gland, sometimes called the master gland, plays a critical role in regulat­ ing growth and development, metabolism, and reproduction. It produces prolactin and other key hormones including The pituitary gland sits in the sella turcica. • growth hormone, which regulates growth • luteinizing hormone and follicle- stimulating hormone, which regulate • adrenocorticotropin (ACTH), which ovulation and estrogen and progester­ stimulates the adrenal glands to pro­ one production in women and sperm duce cortisol, a hormone important in formation and testosterone production metabolism and the body’s response to in men stress The pituitary gland sits in the middle of the • thyrotropin, which signals the thyroid head in a bony box called the sella turcica. gland to produce thyroid hormone, also The optic nerves sit directly above the pitu­ involved in metabolism and growth itary gland. Enlargement of the gland can cause symptoms such as headaches or visual What causes prolactinoma? disturbances. Pituitary tumors may also The cause of pituitary tumors remains impair production of one or more pituitary largely unknown. Most pituitary tumors are hormones, causing reduced pituitary func­ sporadic, meaning they are not genetically tion, also called hypopituitarism. passed from parents to their children. How common is What else causes prolactin prolactinoma? to rise? Although small benign pituitary tumors are In some people, high blood levels of pro­ fairly common in the general population, lactin can be traced to causes other than symptomatic prolactinomas are uncommon. prolactinoma. Prolactinomas occur more often in women than men and rarely occur in children. Prescription drugs. Prolactin secretion in the pituitary is normally suppressed by the What are the symptoms of brain chemical dopamine. Drugs that block the effects of dopamine at the pituitary or prolactinoma? deplete dopamine stores in the brain may In women, high levels of prolactin in the cause the pituitary to secrete prolactin. blood often cause infertility and changes in These drugs include older antipsychotic menstruation. In some women, periods may medications such as trifluoperazine (Stela­ stop. In others, periods may become irregu­ zine) and haloperidol (Haldol); the newer lar or menstrual flow may change. Women antipsychotic drugs risperidone (Risperdal) who are not pregnant or nursing may begin and molindone (Moban); metoclopramide producing breast milk. Some women may (Reglan), used to treat gastroesophageal experience a loss of libido—interest in sex. reflux and the nausea caused by certain Intercourse may become painful because of cancer drugs; and less often, verapamil, vaginal dryness. alpha–methyldopa (Aldochlor, Aldoril), and reserpine (Serpalan, Serpasil), used to In men, the most common symptom of pro­ control high blood pressure. Some antide­ lactinoma is erectile dysfunction. Because pressants may cause hyperprolactinemia, but men have no reliable indicator such as further research is needed. changes in menstruation to signal a problem, many men delay going to the doctor until Other pituitary tumors. Other tumors they have headaches or eye problems caused arising in or near the pituitary may block by the enlarged pituitary pressing against the flow of dopamine from the brain to nearby optic nerves. They may not recognize the prolactin-secreting cells. Such tumors a gradual loss of sexual function or libido. include those that cause acromegaly, a condi­ Only after treatment do some men realize tion caused by too much growth hormone, they had a problem with sexual function. and Cushing’s syndrome, caused by too much cortisol. Other pituitary tumors that do not result in excess hormone production may also block the flow of dopamine. 2 Prolactinoma Hypothyroidism. Increased prolactin levels How is prolactinoma are often seen in people with hypothyroid­ ism, a condition in which the thyroid does treated? not produce enough thyroid hormone. The goals of treatment are to return prolac­ Doctors routinely test people with hyperpro­ tin secretion to normal, reduce tumor size, lactinemia for hypothyroidism. correct any visual abnormalities, and restore normal pituitary function. In the case of Chest involvement. Nipple stimulation also large tumors, only partial achievement of can cause a modest increase in the amount of these goals may be possible. prolactin in the blood. Similarly, chest wall injury or shingles involving the chest wall Medical Treatment may also cause hyperprolactinemia. Because dopamine is the chemical that normally inhibits prolactin secretion, doc­ How is prolactinoma tors may treat prolactinoma with the dop­ diagnosed? amine agonists bromocriptine (Parlodel) or cabergoline (Dostinex). Agonists are drugs A doctor will test for prolactin blood levels that act like a naturally occurring substance. in women with unexplained milk secretion, These drugs shrink the tumor and return called galactorrhea, or with irregular menses prolactin levels to normal in approximately or infertility and in men with impaired sexual 80 percent of patients. Both drugs have function and, in rare cases, milk secretion. been approved by the U.S. Food and Drug If prolactin levels are high, a doctor will test Administration for the treatment of hyper­ thyroid function and ask first about other prolactinemia. Bromocriptine is the only conditions and medications known to raise dopamine agonist approved for the treat­ prolactin secretion. The doctor may also ment of infertility. This drug has been in request magnetic resonance imaging (MRI), use longer than cabergoline and has a well- which is the most sensitive test for detecting established safety record. pituitary tumors and determining their size. MRI scans may be repeated periodically to Nausea and dizziness are possible side assess tumor progression and the effects of effects of bromocriptine. To avoid these therapy. Computerized tomography (CT) side effects, bromocriptine treatment must scan also gives an image of the pituitary but be started slowly. A typical starting dose is is less precise than the MRI. one-quarter to one-half of a 2.5 milligram (mg) tablet taken at bedtime with a snack. The doctor will also look for damage to The dose is gradually increased every 3 to surrounding tissues and perform tests to 7 days as needed and taken in divided doses assess whether production of other pituitary with meals or at bedtime with a snack. Most hormones is normal. Depending on the size people are successfully treated with 7.5 mg of the tumor, the doctor may request an eye a day or less, although some people need exam with measurement of visual fields. 15 mg or more each day. Because bro­ mocriptine is short acting, it should be taken either twice or three times daily. 3 Prolactinoma Bromocriptine treatment should not be those used for prolactinomas, heart valve stopped without consulting a qualified damage has been reported. Rare cases endocrinologist—a doctor specializing in of valve damage have been reported in disorders of the hormone-producing glands. people taking low doses of cabergoline to Prolactin levels rise again in most people treat hyperprolactinemia. Before starting when the drug is discontinued. In some, these medications, the doctor will order an however, prolactin levels remain normal, so echocardiogram. An echocardiogram is a the doctor may suggest reducing or discon­ sonogram of the heart that checks the heart tinuing treatment every 2 years on a trial valves and heart function. basis. Because limited information exists about Cabergoline is a newer drug that may be the risks of long-term, low-dose cabergoline more effective than bromocriptine in nor­ use, doctors generally prescribe the lowest malizing prolactin levels and shrinking tumor effective dose and periodically reassess the size. Cabergoline also has less frequent and need for continuing therapy. People taking less severe side effects. Cabergoline is more cabergoline who develop symptoms of short­ expensive than bromocriptine and, being ness of breath or swelling of the feet should newer on the market, its long-term safety promptly notify their physician because these record is less well defined. As with bro­ may be signs of heart valve damage. mocriptine therapy, nausea and dizziness are possible side effects but may be avoided if Surgery treatment is started slowly. The usual start­ Surgery to remove all or part of the tumor ing dose is .25 mg twice a week. The dose should only be considered if medical therapy may be increased every 4 weeks as needed, cannot be tolerated or if it fails to reduce up to 1 mg two times a week. Cabergoline prolactin levels, restore normal reproduction should not be stopped without consulting a and pituitary function, and reduce tumor qualified