Brief overview
- Symptoms: Mostly signs of too high prolactin levels such as menstrual disorders in women, absence of menstrual periods; in men, loss of libido, impotence; in the case of macroprolactinoma, visual disturbances or, for example, headaches are possible
- Treatment: In many cases, no treatment is necessary. Many prolactinomas requiring treatment respond well to drugs from the dopamine agonist group. Rarely surgery, very rarely radiotherapy
- Causes and risk factors: Uncontrolled division of hormone-producing cells; cause usually unknown; a possible risk of prolactinoma exists, for example, in the hereditary disease multiple endocrine neoplasia type 1.
- Diagnosis: Based on symptoms, medical history, blood values (especially the hormone prolactin: values above 250 micrograms per liter indicate prolactinoma); confirmation by magnetic resonance imaging (MRI)
- Prognosis: Good prognosis, with treatment often complete cure already possible without surgery
What is prolactinoma?
Prolactinoma is the most common tumor of the pituitary gland. It causes the pituitary gland to secrete more of the hormone prolactin. Prolactinoma is possible in both men and women. Most often, prolactinoma develops in women younger than 50 years.
Depending on the size of the tumor, it is referred to as a microprolactinoma (diameter smaller than ten millimeters) or macroprolactinoma (diameter larger than ten millimeters). Most prolactinomas fall into the first category, meaning they are smaller than ten millimeters. They are also usually benign; malignant prolactinomas are very rare. Prolactinomas belong to the pituitary adenomas because they are located in the anterior lobe of the pituitary gland – the adenohypophysis.
The hormone prolactin
During breastfeeding, the high prolactin level often suppresses ovulation and thus prevents another pregnancy. However, the decisive factor is, among other things, how often and how long the child is breastfed. Breastfeeding is not a reliable method of contraception.
What are the symptoms?
Prolactinoma causes symptoms in two possible ways:
- It produces a lot of prolactin, which affects the action of other hormones.
- It grows and displaces nearby tissue, such as nerves leading from the eye to the brain.
Prolactin-producing prolactinoma causes sexual dysfunction in men as well as in pre-menopausal women. Post-menopausal women usually do not have any symptoms with a prolactinoma because the ovaries have already stopped functioning by then.
Furthermore, if in some cases the tumor itself does not produce prolactin, the symptoms are not specific for prolactin overproduction, but only for missing other hormones.
Prolactinoma: symptoms in pre-menopausal women.
High prolactin levels in women of childbearing age inhibit ovulation, resulting in irregular or even absence of menstruation (amenorrhea). About ten to 20 percent of women with missed periods have excessively high prolactin levels. Because of the cycle disturbances, women with prolactinoma have difficulty getting pregnant. Other symptoms include vaginal dryness and hot flashes.
Prolactinoma also stimulates milk production and secretion. In about 24 percent of women with high prolactin levels, small amounts of milk leak from the breast (galactorrhea) even though the woman is not pregnant or breastfeeding.
Prolactinoma: symptoms in post-menopausal women
In women after menopause, hormone-producing prolactinoma usually does not show any symptoms. This is because prolactin then no longer has any influence on the menstrual cycle. Affected women only notice a prolactinoma when it has grown so large that it affects neighboring tissue, causing headaches, visual disturbances or interference with other hormones.
In some cases, it is discovered purely by chance if for some other reason the head is examined with an imaging procedure (magnetic resonance imaging, MRI).
Prolactinoma: symptoms in men
In men, a hormone-producing prolactinoma also causes excessive prolactin levels and inhibits the gonads, in this case the testes. These consequently produce fewer sperm and testosterone, the most important sex hormone in men. Typical symptoms are loss of libido, impotence, infertility and listlessness.
If the prolactinoma has existed for a long time, muscle mass decreases in many cases. In addition, it is often observed that pubic hair and beard growth recede. As in women, bone mass also decreases in men, especially as a long-term consequence of prolactinoma. Long-standing prolactinoma thus often leads to osteoporosis.
Macroprolactinoma causes further symptoms
If the prolactinoma becomes larger than one centimeter and thus a macroadenoma, it may press on neighboring structures of the brain. Often, the optic nerve comes under pressure, resulting in visual disturbances. In most cases, affected individuals have bilateral lateral visual field loss (blink hemianopsia). In some cases, only one eye is affected.
Due to the pressure of the tumor on brain structures, headaches are also a possible symptom.
How can a prolactinoma be treated?
Not every prolactinoma requires treatment. If it is very large or causes symptoms, treatment is advisable. If the prolactinoma is small and does not cause symptoms, treatment is often not necessary. The doctor and patient together weigh the benefits and risks of treatment options.
Drug treatment
If treatment is necessary, the prolactinoma usually responds very well to the administration of so-called dopamine agonists. These are drugs that trigger a similar effect in the body as the endogenous neurotransmitter dopamine. In most cases, dopamine agonists lower the prolactin level and cause the prolactinoma to shrink or even disappear completely.
Dopamine agonists are usually taken for several years. Prolactin levels are continuously monitored during this time.
For prolactinoma, administration of approximately the following dopamine agonists is possible:
Bromocriptine
Bromocriptine has been used for prolactinoma treatment for about 30 years. It is taken twice a day and is very effective in rapidly lowering prolactin levels. However, bromocriptine causes many side effects: Sufferers often complain of dizziness, nausea, and a stuffy nose. However, many of the side effects can be prevented by taking the drug before meals or at bedtime.
Cabergoline
Cabergoline is taken only once or twice a week and causes fewer side effects. It usually lowers prolactin levels by about 90 percent, making it the treatment of choice. However, it is not recommended for women who want to become pregnant.
Drug treatment during pregnancy
- When should dopamine agonist therapy be stopped?
- What is the risk of prolactinoma growing during pregnancy?
- What are the treatment options if the prolactinoma grows again?
- Is it possible for me to breastfeed my child afterwards?
If vision problems or headaches occur during pregnancy, this may be a sign that the prolactinoma has grown again. To detect this early, an eye test is done every month. After treatment of prolactinoma, it is possible for most women to become pregnant normally.
Surgical treatment
If the patient does not respond to dopamine agonists, the prolactinoma may be surgically removed. In women with very large macroprolactinoma, surgery is the treatment of choice. The risk of the prolactinoma continuing to grow during a possible pregnancy is too great in this case.
The elevated prolactin levels usually decrease immediately after surgery, sometimes even to normal levels in the case of microadenomas.
Radiotherapy
Radiation therapy is rarely used, and it is used when drug and surgical therapy measures have not shown sufficient success. Radiation often causes the prolactinoma to shrink and the blood prolactin level to decrease.
However, the therapy often takes years to show its full effect and also has many side effects such as nausea, fatigue, loss of the sense of taste and smell, and hair loss. In addition, half of patients who have received radiation therapy develop pituitary dysfunction within ten years, with lowered blood levels of pituitary hormones.
Causes and risk factors
A prolactinoma develops when a lactotrophic cell mutates and begins to divide uncontrollably. This eventually results in a large mass of altered cells, all of which produce prolactin – the prolactin level increases. About ten percent also produce growth hormone in addition to prolactin.
In most cases, prolactinoma develops without an identifiable cause. In rare cases, it develops as part of a hereditary disease, multiple endocrine neoplasia type 1 (MEN 1).
Examinations and diagnosis
There are several tests to detect prolactinoma. The appropriate professional to see if prolactinoma is suspected is an endocrinologist, a specialist in hormone balance and metabolism. The doctor first takes the medical history (anamnesis). In doing so, he asks the following questions, for example:
- Are you pregnant?
- Are you taking estrogens or certain medications such as risperidone, metoclopramide, antidepressants, cimetidine, methyldopa, reserpine or verapamil?
- Do you have any visual disturbances? If so, what kind?
- Are you sensitive to cold, listless or tired?
The doctor will then perform a physical examination. He will examine you for visual disturbances such as visual field defects, signs of hypothyroidism and estrogen or testosterone deficiency.
The next step is for the doctor to take a blood sample to measure the prolactin level. The blood test should be done at the earliest one to two hours after waking up, as the prolactin level is higher during sleep than when awake.
Other causes of high prolactin levels
An elevated prolactin level (hyperprolactinemia) is not always necessarily caused by a prolactinoma. In addition to stress and other diseases, certain medications often cause high prolactin levels, for example, so-called dopamine antagonists such as metoclopramide (for nausea and vomiting) or some agents used to treat mental illness (such as antidepressants, neuroleptics).
Course of the disease and prognosis
If it is a microprolactinoma, drug therapy with dopamine agonists can almost always achieve a normal prolactin level. If surgery is necessary, this too usually leads to normal prolactin levels in the long term for a small prolactinoma. Nevertheless, it is possible that a relapse may occur later. This is also true in the case of a large prolactinoma (macroprolactinoma).
Prevention
After successful therapy with medication or surgery of a prolactinoma, regular control examinations help to detect a possible recurrence of the tumor in time. Even small prolactinomas that do not in themselves require treatment can be monitored in this way to detect sudden growth at an early stage.
