Patient information: High prolactin levels and prolactinomas (Beyond the Basics)
- Peter J Snyder, MD
Peter J Snyder, MD
- Editor-in-Chief — Endocrinology
- Section Editor — Pituitary Disease; Male Reproductive Endocrinology
- Professor of Medicine
- University of Pennsylvania School of Medicine
HIGH PROLACTIN OVERVIEW
Prolactin-producing adenomas (also called “prolactinomas”) are benign (non-cancerous) tumors of the pituitary gland that produce prolactin and thereby cause higher than normal blood prolactin concentrations. They can cause symptoms, either when the high blood prolactin concentration interferes with the function of the ovaries or testicles or, less commonly, when the adenoma grows large enough to compress nearby structures in the head, such as the nerves to the eyes.
Prolactinomas occur in both men and women but are more commonly diagnosed in women who are less than 50 years than in older women or men.
Prolactinomas can usually be treated successfully with medication alone. Medication lowers the prolactin level in the blood substantially, often to normal, and also usually reduces adenoma size. However, a minority of these adenomas do not respond to medication and must be treated with surgery or, less commonly, radiation therapy.
CAUSES OF HIGH PROLACTIN
The pituitary is a small gland in the middle of the head just below the brain (figure 1). The pituitary contains lactotroph cells that produce prolactin, the hormone that stimulates lactation (formation of breast milk). Prolactin-producing adenomas develop when one of these normal cells develops a mutation that allows the cell to divide repeatedly, resulting in a large number of cells that produce an excessive amount of prolactin. About 10 percent produce growth hormone as well as prolactin.
Most prolactinomas occur sporadically but, rarely, they occur in families as part of a condition called the multiple endocrine neoplasia type 1 (MEN 1) syndrome.
Most prolactinomas remain small, less than 1 centimeter (0.4 inches) in diameter and are called microadenomas. A minority grow larger, occasionally to several centimeters, and are called macroadenomas.
The symptoms of prolactinomas fall into two categories: those that result from elevated blood prolactin levels, and those that result from compression of surrounding tissues.
Symptoms caused by elevated blood prolactin — Elevated blood prolactin interferes with the function of the ovaries in women and the testicles in men. Therefore, it causes symptoms in premenopausal women and in men, but not in postmenopausal women, whose ovaries have stopped functioning.
Women — When a high blood prolactin concentration interferes with the function of the ovaries in a premenopausal woman, secretion of estradiol, the main estrogen, decreases. Symptoms include irregular or absent menstrual periods, infertility, menopausal symptoms (hot flashes and vaginal dryness) and, after several years, osteoporosis. High prolactin levels can also cause milk discharge from the breasts.
Men — When a high blood prolactin concentration interferes with the function of the testicles, the production of testosterone (the main male sex hormone) and sperm decrease. Low testosterone causes decreased energy, sex drive, muscle mass and strength, and blood count. If levels remain low for several years, bone strength may decrease (osteoporosis). High blood prolactin also causes difficulty in getting an erection, as well as breast tenderness and enlargement.
Symptoms caused by compression of surrounding tissue — Large adenomas can cause symptoms by pressing on nearby structures in the head. Pressure on nerves to the eyes can impair vision, especially peripheral (side) vision. Pressure on the pituitary gland can decrease production of the hormones that stimulate the thyroid gland and adrenal glands, leading to underactivity of the those glands. Pressure can also cause headaches.
DIAGNOSIS OF PROLACTINOMA
A prolactinoma is diagnosed based upon an elevated blood level of prolactin and evidence of a mass in the pituitary gland, as seen on a magnetic resonance imaging (MRI) scan. Because other conditions can cause an elevated prolactin, those causes must be evaluated as well.
Measurement of prolactin — The prolactin level can be measured in a single blood sample. The result can range from slightly elevated to a thousand times the upper limit of normal. In general, larger adenomas cause higher prolactin levels.
Magnetic resonance imaging (MRI) — MRI is the best test for identifying masses in or near the pituitary gland, although MRI cannot determine if the mass is a pituitary adenoma or another abnormality. Furthermore, some small adenomas (microadenomas) cannot be detected by MRI, and not all adenomas secrete prolactin or other hormones.
Evaluating other causes — Other causes of a high blood prolactin level include certain medications, especially those used to treat psychiatric conditions and estrogens taken by mouth, and underactivity of the thyroid (hypothyroidism).
PROLACTINOMA TREATMENT OPTIONS
The goals of treatment are to lower the level of prolactin in the blood to normal and to decrease the size of a large adenoma, especially if it is compressing surrounding structures. It is important that the clinician and patient discuss the possible benefits and risks of treatment.
Not all prolactinomas require treatment. If it is large or causing symptoms, it should probably be treated, but if it is small and is not causing symptoms, it does not need to be treated.
When treatment is necessary, most prolactinomas respond well to therapy with medications called dopamine agonists. If an adenoma does not respond to any of these medications or if the medication causes intolerable symptoms, other treatments should be considered.
MEDICATIONS TO TREAT PROLACTINOMAS
A dopamine agonist is the best first treatment for a prolactinoma of any size. Two dopamine agonists are currently available for this purpose in the United States, cabergoline and bromocriptine, and another one as well in other countries, quinagolide.
Bromocriptine — Bromocriptine has been used for 30 years to treat prolactinomas. It is taken twice a day. While it is usually very effective in lowering blood prolactin levels, it can cause side effects, including dizziness, nausea, and nasal stuffiness. Many of the side effects can be avoided by taking the medication with meals or at bedtime and by starting with a very low dose (one-fourth to one-half tablet).
Cabergoline — Cabergoline is taken once or twice a week, and is much less likely to cause nausea compared with other dopamine agonists. It may be effective for treating prolactinomas that are resistant to bromocriptine. For all these reasons, cabergoline is the best first choice, except in women who are trying to become pregnant. (See 'Becoming pregnant' below.)
Effectiveness of dopamine agonists — Dopamine agonists are very effective for decreasing prolactin levels and the size of most prolactinomas. Cabergoline, which appears to be the most effective dopamine agonist, lowers prolactin levels in about 90 percent of people who have prolactinomas, often to a level that is normal. It also usually decreases the size of micro- and macroadenomas to normal. Prolactin levels usually fall within the first two to three weeks of treatment, but detectable decreases in adenoma size require more time, usually several weeks to months. When the adenoma affects vision, improvement in vision may begin within days of starting treatment.
If the prolactin level decreases to normal or near normal levels, the effects of the elevated prolactin are reversed. The upper normal value for serum prolactin in most laboratories is about 20 ng/mL (20 mcg/L SI units). In premenopausal women, ovarian function returns, estrogen levels increase, menstrual periods return, and fertility returns. In men, testicular function returns, causing an increase in energy, sex drive, muscle mass, blood count, and bone calcium. The ability to have an erection returns and, eventually, breast enlargement regresses.
Side effects of drug therapy — The major side effects of dopamine agonists are nausea, lightheadedness after standing, and mental fogginess. These side effects are most likely to occur when treatment first begins and when the dose is increased. They can be minimized by starting with a small dose, increasing the dose slowly if needed, using small doses more frequently, and taking the drug with food or at bedtime. In women, intravaginal administration can decrease or prevent nausea. Psychiatric effects and severe constipation sometimes occur, but they are uncommon. Unfortunately, starting with a low dose does not prevent them, and if they occur, they do not seem to get better with time.
Cabergoline has been associated with valvular heart disease in people with Parkinson disease who took much larger doses (more than 20 mg a week) than used for prolactinomas (0.5 to 2 mg a week). So far, there are no confirmed cases of valvular heart disease in people being treated for hyperprolactinemia. However, experts recommend using the lowest dose of cabergoline necessary to lower prolactin to normal; they also recommend doing ultrasound (echocardiogram) of the heart valves in patients with prolactinomas who need higher than usual doses of cabergoline.
Heart valve problems have not been seen in people taking bromocriptine, even in high doses.
How long is medication needed? — If the prolactin level remains normal and no adenoma is seen on magnetic resonance imaging (MRI) for two or more years, a trial period without medication can be considered. However, the high prolactin level often recurs after the medication is stopped. Monitoring of the prolactin level and, less frequently, the size of the pituitary, would continue during this time. If the prolactin levels begin to rise or the adenoma grows in size, a dopamine agonist may be recommended.
If the dopamine agonist is not effective in lowering the prolactin level, or if the person cannot tolerate the side effects, surgery to remove the adenoma may be considered. (See 'Surgery for lactotroph adenoma' below.)
Considerations specific to women
Drug therapy and menopause — Women who have microadenomas usually do not have to continue taking dopamine agonists after menopause. The prolactin is usually measured a few months after treatment is stopped to be sure that it is not substantially higher than before treatment. This is usually done once per year for a few years and less often thereafter. Women who have macroadenomas should continue taking dopamine agonists after menopause to keep the size of the adenoma from increasing.
Estrogen and progestin — Estrogen, in combination with progestin, is a treatment option for women who have small lactotroph adenomas, especially women who have intolerable side effects with dopamine agonists and those who do not want to become pregnant.
The rationale for estrogen treatment is that the only known harmful effect of an elevated blood prolactin in a woman is decreased ovarian function, including diminished secretion of estrogen. Estrogen doses and regimen are discussed in a separate topic review. (See "Patient information: Menopausal hormone therapy (Beyond the Basics)".)
The prolactin concentration should be monitored periodically because of the small chance that the adenoma could grow. Estrogen and progestin treatment are not recommended as the only treatment in women with macroadenomas (>1 cm).
Becoming pregnant — A woman who has a lactotroph adenoma and wishes to become pregnant can usually do so with little risk to herself or her developing child. However, the woman should discuss her desire to become pregnant with an endocrinology specialist before attempting to become pregnant. Issues to address include which treatment is best before attempting to become pregnant, when to discontinue dopamine agonist treatment, the chance that the adenoma will grow during pregnancy, what would be done if it does grow, and whether or not breastfeeding is advisable. These considerations are influenced greatly by whether the adenoma was less than 1 cm (microadenoma) or greater than 1 cm (macroadenoma) prior to treatment.
Microadenomas rarely increase in size during the course of pregnancy. The best treatment to restore fertility in women with a microadenoma is a dopamine agonist. Bromocriptine does not appear to increase the risk of miscarriage or birth defects when it is taken to restore fertility and discontinued early in pregnancy.
Less information is available about the safety of cabergoline, although the available information does not indicate that it increases the risk of birth defects. Bromocriptine, therefore, appears to be the safest dopamine agonist to use to restore fertility, although a woman who has severe side effects from bromocriptine could reasonably choose cabergoline. Dopamine agonist treatment should be discontinued as soon as pregnancy is diagnosed. There is insufficient information about the safety of these medications during later stages of pregnancy.
If dopamine agonists do not lower prolactin sufficiently to restore ovulation, other medications, such as clomiphene citrate or gonadotropins, may be recommended to induce ovulation. Once pregnancy is diagnosed, the dopamine agonist should be discontinued. (See "Patient information: Ovulation induction with clomiphene (Beyond the Basics)".)
During the course of the pregnancy it is possible for the adenoma to increase in size. To monitor for an increase in size, the woman should let her healthcare provider know if she develops new or worsening headaches or worsening vision.
Macroadenomas may increase in size during the course of pregnancy. Signs that the adenoma is growing include new or worsening headaches or changes in vision.
If vision worsens, the woman should see an ophthalmologist. An MRI may be recommended to determine if there has been an increase in adenoma size. If so, bromocriptine is usually recommended to decrease the size. There is little information about the effect of bromocriptine on the fetus during the second and third trimesters; however, the available information suggests that bromocriptine does not harm the fetus. If necessary, surgery to remove the adenoma can be performed during the second trimester.
If the adenoma was greater than 2 cm in diameter or was affecting vision prior to treatment, surgery should be considered before the woman tries to become pregnant. Surgery is recommended because growth of the adenoma during pregnancy can potentially interfere with vision or cause headaches. Following surgery, a dopamine agonist may be recommended to restore fertility. Alternatively, if the adenoma is very sensitive to cabergoline or bromocriptine, a low dose can be continued during the entire pregnancy or it can be administered only if the adenoma increases sufficiently to cause visual symptoms during the pregnancy. (See 'Surgery for lactotroph adenoma' below.)
Breastfeeding — If a woman wishes to breastfeed, she should not resume dopamine agonist treatment until breastfeeding is completed. If there was an increase in the size of the adenoma during pregnancy sufficient to cause visual symptoms, most experts recommend that the woman not breastfeed so that she may restart dopamine agonist treatment immediately after delivery.
SURGERY FOR LACTOTROPH ADENOMA
Surgery is an option when dopamine agonists are ineffective or not tolerated. Surgery may also be the best choice for a woman with very large macroadenoma that is not entirely responsive to dopamine agonists who wants to become pregnant, because dopamine agonists must be discontinued during pregnancy, and during this time the adenoma may grow.
During surgery, a small incision is made in the nose (figure 2). The incision is extended through the sphenoid sinus, allowing the surgeon to visualize and remove the adenoma. Most experienced pituitary neurosurgeons now perform this procedure using an endoscope (a thin, lighted tube with a camera).
Surgery can often reduce the blood prolactin concentration, sometimes to normal. This is more likely for a microadenoma than a macroadenoma. Even if the prolactin is lowered to within the normal range shortly after surgery, the level may become elevated in the next several years. Potential side effects of surgery include worsening of vision, hemorrhage, and meningitis, which are all uncommon, and hormonal deficiencies. The risk of complications is less when the procedure is performed by a surgeon who has had significant experience operating on the pituitary gland.
Radiation therapy — Radiation therapy can shrink prolactinomas and lower blood prolactin levels, but these effects usually take several years. Therefore, radiation is used only as secondary treatment of macroadenomas, to prevent regrowth of substantial residual tissue that could not be removed during surgery of a macroadenoma that is not responsive to dopamine agonists.
The possible side effects of radiation treatment include transient nausea, fatigue, loss of taste and smell, and loss of hair at specific sites on the scalp. About half of those who receive pituitary radiation therapy develop pituitary hormone deficiencies within 10 years.
WHERE TO GET MORE INFORMATION
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Causes of hyperprolactinemia
Causes, presentation, and evaluation of sellar masses
Clinical manifestations and evaluation of hyperprolactinemia
Management of lactotroph adenoma (prolactinoma) during pregnancy
Incidentally discovered sellar masses (pituitary incidentalomas)
Treatment of hyperprolactinemia due to lactotroph adenoma and other causes
The following organizations also provide reliable health information.
●National Library of Medicine
●National Institute of Diabetes and Digestive and Kidney Disorders
●Hormone Health Network
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