Prolactinoma is a condition in which a noncancerous tumor (adenoma) of the pituitary gland in your brain overproduces the hormone prolactin. The major effect of increased prolactin is a decrease in normal levels of sex hormones — estrogen in women and testosterone in men.
Although prolactinoma isn’t life-threatening, it can cause visual impairment, infertility and other effects. Prolactinoma is one of several types of tumors that can develop in your pituitary gland.
Doctors often are able to effectively treat prolactinoma with medications to restore your prolactin level to normal. Surgery to remove the pituitary tumor also may be an option to treat prolactinoma.
The pituitary and your endocrine system
The pituitary gland is a small bean-shaped gland located at the base of your brain. Despite its small size, the pituitary gland influences nearly every part of your body. Its hormones help regulate important functions such as growth, blood pressure and reproduction.
The pituitary gland is part of your endocrine system, which consists of other glands that produce hormones that regulate many processes throughout your body. Besides the pituitary gland, the endocrine system includes the thyroid gland, parathyroid glands, adrenal glands, pancreas, ovaries (in females) and testicles (in men).
Prolactinoma is one type of tumor that develops in the pituitary gland. Some pituitary tumors may produce hormones in excess (functioning pituitary tumors), but most don’t (nonfunctioning pituitary tumors).
The cause of pituitary tumors remains unknown. Although these pituitary tumors are almost always noncancerous (benign), which means they don’t spread to other parts of your body, they can increase in size. Because they grow in such limited space, they can compress and damage the normal pituitary tissue, interfering with hormone production. A tumor can also compress your optic nerves, slowly causing a loss of vision.
Other causes of prolactin overproduction
Overproduction of prolactin can result from causes other than a prolactinoma, including:
Medications. The secretion of prolactin in your pituitary gland normally is suppressed by the brain chemical dopamine. Drugs that block the action of dopamine in your pituitary gland or that decrease the amount of dopamine that’s produced and stored in your brain may cause excess prolactin production, including:
- Tranquilizers, such as trifluoperazine and haloperidol
- Anti-nausea and gastroesophageal reflux disease (GERD) drugs, such as metoclopramide (Reglan)
- High blood pressure (hypertension) medications, such as methyldopa and reserpine.
Other pituitary tumors. Other tumors in or near your pituitary gland, such as nonfunctioning tumors and those that can cause overproduction of growth hormone (acromegaly) or the hormone cortisol (Cushing’s disease), may block the flow of dopamine from your brain to your pituitary gland.
Hypothyroidism. Excess production of prolactin may occur in people with severe and long-standing hypothyroidism — insufficient hormone production by your thyroid gland.
Pregnancy, breast-feeding and breast stimulation. During pregnancy, a woman’s prolactin level normally increases to prepare her breasts for milk production. After delivery, the prolactin level returns to normal, but increases again each time a baby feeds. Breast stimulation unrelated to pregnancy or breast-feeding also may cause breast discharge and a mild increase in the prolactin level.
The signs and symptoms of prolactinoma result from excessive prolactin in your blood (hyperprolactinemia) and, if the tumor is large, from the pressure of the tumor on surrounding tissues. Because elevated levels of the hormone prolactin cause disruption of the reproductive system (hypogonadism), some of the signs and symptoms of prolactinoma are unique for each sex.
In some cases, there aren’t any signs and symptoms. But when there are, prolactinoma symptoms may include:
- Irregular menstrual periods (oligomenorrhea) or lack of menstrual periods (amenorrhea)
- Milky discharge from the breasts (galactorrhea) when not pregnant or breast-feeding
- Painful intercourse due to vaginal dryness
- Low bone density
- Reduced hormone production by the pituitary gland (hypopituitarism) as a result of tumor pressure
- Loss of interest in sexual activity
- Visual disturbances
Women tend to notice signs and symptoms earlier than men do, when tumors are smaller in size, probably because they’re alerted that there might be a problem due to missed or irregular menstrual periods. Men, on the other hand, tend to notice signs and symptoms later, when tumors are much larger and more likely to cause headache or vision problems.
Blood tests can detect the overproduction of prolactin as a result of a pituitary tumor. Blood tests can also detect if levels of other hormones controlled by the pituitary are within the normal range. Additionally, your doctor may recommend:
- Brain imaging. Your doctor may be able to detect a pituitary tumor on an image generated by a computerized tomography (CT) or magnetic resonance imaging (MRI) scan of your brain.
- Tests of your vision. Such tests can determine if growth of a pituitary tumor has impaired your sight or peripheral vision.
In addition, your doctor may refer you for more extensive testing with a doctor who specializes in treating disorders of the endocrine system
Specific goals in the treatment of prolactinoma include:
- Return the production of prolactin to normal levels
- Restore normal pituitary gland function
- Eliminate galactorrhea
- Reduce the size of the pituitary tumor
- Eliminate any signs or symptoms from tumor pressure, such as headaches or vision problems
Prolactinoma treatment consists of two main therapies, medications and surgery:
Oral medications often can decrease the production of prolactin and eliminate symptoms. Medications may also shrink the tumor. However, long-term treatment with medications is generally necessary.
Doctors use drugs known as dopamine agonists to treat prolactinoma. These drugs mimic the effects of dopamine — the brain chemical that normally controls prolactin production — but are much more potent and long lasting. Commonly prescribed medications include bromocriptine (Parlodel) and cabergoline (Dostinex). These drugs decrease prolactin production and may shrink the tumor in most people with prolactinoma.
Bromocriptine is the preferred drug when treating women who want to restore their fertility because its safety in pregnancy is well established. Common side effects of these medications include lightheadedness, nausea and nasal stuffiness. However, these side effects often can be minimized if your doctor starts you with a very low dose of medication and gradually increases the dose.
If medication effectively shrinks the tumor and your prolactin level remains normal afterward, you may be able to eventually stop taking the medication. Your doctor can offer you advice on when this may be possible for you.
The type of surgery you have depends largely on the location and the size of your tumor. Most people who need surgery have a transsphenoidal procedure. In this surgery, the tumor is removed through the nasal cavity. Complication rates from this type of surgery are low because no other areas of the brain are touched during surgery, and this surgery leaves no visible scars. However, transsphenoidal surgery may not be best for some large tumors, or for tumors that have spread to nearby brain tissue. If this is the case for you, you may need a transcranial procedure, also known as a craniotomy. This procedure involves accessing the tumor through the upper part of the skull.
The outcome of surgery depends on the size and location of the tumor and if your prolactin level is extremely high. The higher the prolactin level, the slimmer the chance that your prolactin production will return to normal after surgery. Surgery corrects the prolactin level in most people with small pituitary tumors. However, many pituitary tumors recur within five years after surgical removal. For people with larger tumors that can only be partially removed, drug therapy often can return the prolactin level to a normal range after surgery.
Complications of prolactinoma may include:
- Vision loss. Left untreated, a prolactinoma may grow large enough to compress your optic nerves. This usually begins with loss of peripheral vision, but can progress to blindness.
- Hypopituitarism. With larger prolactinomas, pressure on the normal pituitary gland can cause dysfunction of other hormones controlled by the pituitary, resulting in hypothyroidism, adrenal insufficiency and growth hormone deficiency.
- Bone loss (osteoporosis). Too much prolactin can reduce production of the hormone estrogen, resulting in decreased bone density and increasing your risk of osteoporosis.
- Pregnancy complications. During a normal pregnancy, a woman’s pituitary gland enlarges and prolactin production increases. A woman who has a large prolactinoma and becomes pregnant may experience additional pituitary growth and associated signs and symptoms, such as headaches, changes in vision, nausea, vomiting, excessive thirst or urination, and extreme fatigue.If you have a prolactinoma and you want to become or you already are pregnant, discuss the situation with your doctor because adjustments in your treatment and monitoring may be necessary.