Prolactinoma occurs when a benign tumor, called an adenoma, affects the pituitary gland located at the base of the brain. The pituitary gland regulates your body’s hormone production and influences blood pressure, growth, and reproductive systems. The major effect is decreased levels of some sex hormones — estrogen in women and testosterone in men. Prolactinoma is the most common type of pituitary tumor that produces a hormone. It makes up at least 30% of all pituitary adenomas. Almost all pituitary tumors are noncancerous (benign).
The pituitary tumor results in the overproduction of the hormone prolactin, and for women, excessive prolactin levels cause the suppression of estrogen. Prolactinoma in men results in a reduction in testosterone.
In women, prolactin stimulates the breast to produce milk and has many other functions such as regulating moods. Prolactin levels are usually higher during pregnancy and after childbirth. After the delivery of a baby, a mother’s prolactin levels come down to normal a few weeks after breastfeeding is discontinued. Each time the milk is dispensed, prolactin levels rise, a cycle process to maintain milk production.
Most cases affect women in their 20s and early 30s, but the condition can occur at any age. While prolactinoma is benign, it can cause unpleasant symptoms. With proper treatment, many of these symptoms can be effectively managed.
Symptoms of Prolactinoma
An excess of prolactin production in the bloodstream can cause sexual and hormonal problems. A prolactinoma affects the reproductive systems of both sexes by decreasing the level of sex hormones. For women, this causes symptoms such as:
- Irregular or no menstrual periods (amenorrhea)
- Increase or thickening of body hair and facial hair
- Cloudy white discharge from the nipples, unrelated to pregnancy or breastfeeding
- Vaginal dryness
- Painful sexual intercourse
- Decreased desire for sex
- Low bone density, osteopenia, or osteoporosis
Additionally, the pressure of a large tumor in the brain, even when it is benign, can cause uncomfortable symptoms such as:
- Vision problems
Usually, women tend to notice hormone-related symptoms before they experience headaches and vision problems. Your doctor will test for prolactin blood levels in women with unexplained milk secretion, or irregular menses or infertility, This is because the tumor will affect the function of the pituitary gland first, and then press on the surrounding brain tissue later as it grows larger.
Other Causes of Prolactinoma
Although most cases of prolactinoma are caused by a tumor on the pituitary gland, there are other conditions that could lead to an overproduction of prolactin and result in the same symptoms. Such conditions include:
- Certain medications
- Trauma to the chest
Complications of Prolactinoma
If left untreated, a prolactinoma can cause more serious health problems. Prolactin floods the bloodstream, reducing estrogen and causing reproductive problems. As the adenoma grows, it can threaten the surrounding tissues.
Too much prolactin can reduce the production of the hormones estrogen and testosterone, resulting in decreased bone density and an increased risk of osteoporosis.
The pituitary gland controls many other hormones aside from prolactin. 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.
During a normal pregnancy, the production of estrogen increases. If you are pregnant and have a large prolactinoma, these high levels of estrogen may cause tumor growth and associated signs and symptoms, such as headaches and changes in vision.
A prolactinoma may grow large enough to block the optic nerve, leading to a loss of vision.
If you believe you have a prolactinoma, make an appointment with your gynecologist. Keep a log of your menstrual cycle, the details of any symptoms, and when you began to experience these symptoms.
Your health care doctor will conduct a physical exam and take a blood test to look for an excess of prolactin. Prolactinoma is diagnosed through a blood test. Additional tests rule out other causes of high prolactin levels, such as medications or thyroid problems. A magnetic resonance imaging (MRI) can usually detect a tumor and its size on the pituitary gland. Computed Tomography (CT scan) also gives an image of the pituitary, but it is less sensitive than the MRI. If prolactin is high, a doctor will test thyroid function and ask first about other conditions and medications known to raise prolactin secretion. Women in their reproductive years may be given a pregnancy test. A doctor will test for prolactin blood levels in women with unexplained milk secretion (galactorrhea), or irregular menses or infertility,
The doctor will also look for damage to surrounding tissues and perform tests to assess whether the production of other pituitary hormones is normal. Depending on the size of the tumor, the doctor may request an eye exam with a measurement of visual fields.
If you are pregnant or trying to get pregnant, let your gynecologist know. Your pregnancy may aggravate your prolactinoma.
Medical treatments for prolactinoma aim to restore the normal function of the pituitary gland and reduce the size of the tumor. If treatment is successful, this should decrease the production of prolactin back to normal levels and relieve associated symptoms. If medical therapy is effective, women with a small prolactinoma, can usually conceive and have a normal pregnancy.
If your gynecologist believes you have a prolactinoma, it’s likely that he or she will refer you to an endocrinologist for medical treatment. To treat prolactinomas includes one or two primary methods – medication and surgery. Occasionally, radiation therapy is necessary if a prolactinoma does not respond to medication.
Dopamine agonists are drugs that mimic dopamine and they can help regulate the production of prolactin, restore fertility, and reduce the size of an adenoma. Cabergoline and bromocriptine are two popular choices. Cabergoline seems to be a more effective treatment, but bromocriptine is typically the best choice for women who wish to become pregnant.
If you do become pregnant, your specialist will probably take you off the medication. The long-term effects of these drugs on pregnancy are not yet well-understood.
The side effects of dopamine agonists include:
- Nasal congestion
Surgery is usually only an option after the medication is found to be ineffective. Removal of the tumor can decrease the pressure on the surrounding brain tissue and can help restore normal levels of prolactin in the bloodstream, but this is usually only a temporary fix, especially if the tumor was large. Many tumors return in about five years. Surgery in combination with medication can be more effective in regulating hormone levels. The higher the prolactin level before surgery, the lower the chance of normalizing serum prolactin. The serum is the portion of the blood used in measuring prolactin levels.