What is prolactin?
Prolactin is a hormone made by the pituitary gland; a pea-sized organ found at the base of the brain. The main function of prolactin is to stimulate lactation (breast milk production) after childbirth, so having high prolactin levels in pregnancy is normal. Production of prolactin is controlled by two main hormones: dopamine and estrogen. These hormones send a message to the pituitary gland primarily indicating whether to begin or cease the production of prolactin. Dopamine restrains the production of prolactin, while estrogen increases it.
Hyperprolactinemia is a condition in which a person has higher than normal levels of the hormone prolactin in the blood. Hyperprolactinemia can lead to menstrual disturbances, estrogen deficiency and testosterone deficiency, infertility, and breast milk production (galactorrhea).
Prolactin can also interfere with other pituitary hormones—luteinizing hormone and follicle-stimulating hormone—that normally stimulate the function of ovaries and testes. Therefore, high prolactin causes low estrogen in women and decreases fertility. It can also result in bone loss and osteoporosis.
What are the symptoms of hyperprolactinemia?
Women may have infertility, decreased sex drive, bone loss, vaginal dryness, painful intercourse, problems with ovulation and menstruation, production of breast milk when not pregnant or nursing.
What are the common causes of hyperprolactinemia?
One common cause of hyperprolactinemia is a pituitary gland tumor that produces prolactin called a prolactinoma. These tumors can be large or small and are usually benign, meaning they are not cancerous. Small tumors (smaller than 1 cm) are called mircoprolactinomas and larger tumors (more than 1 cm) are called macroprolactinomas. Large tumors can also cause headaches, vision problems, or both.
Several prescription medications can also increase prolactin levels. These include medications for:
Mental health disorders (antipsychotics such as Risperdal and Haloperidol)
Nausea and vomiting
Contraception (Birth Control Pills)
Menopausal symptoms (estrogen)
High blood pressure (calcium-channel blockers and methyldopa)
Depression (tricyclic and SSRI antidepressants)
Other causes include:
Hypothyroidism or underactive thyroid
Pregnancy and lactation
Chest-wall injuries or other conditions that affect the chest wall, such as shingles, surgical scars or even a too tight bra)
Chronic liver and kidney diseases
Other tumors and diseases affecting the pituitary gland, or radiation treatment for tumors on or near the pituitary.
Larger pituitary growths that do not produce prolactin and other diseases, injury or radiation in the pituitary area may also cause hyperprolactinemia but decreasing the amount of dopamine that flows from the brain to the pituitary gland (dopamine normally decreases prolactin)
Sometimes, no cause for hyperprolactinemia can be found.
How is hyperprolactinemia diagnosed?
A blood test is used to detect excess prolactin. Levels are sometimes higher if you have eaten recently or are under stress and the test may need to be repeated. If prolactin levels are high, more tests are usually done to check for other hormones including thyroid hormone levels and to rule out pregnancy in women. Low thyroid (hypothyroidism) sometimes causes hyperprolactinemia. A test for an abnormal form of prolactin (macroprolactin) might also be needed. Macroprolactin does not cause any health problems.
If a pituitary tumor is suspected, an MRI (magnetic resonance imaging) of the brain and pituitary is often the next step. Using a special machine that creates images of body tissues, an MRI can reveal a pituitary tumor and show its size.
What treatments are available for hyperprolactinemia?
Treatment is based on the cause. Treatment options include:
Prescription Medications: Medicines called dopamine agonists like bromocriptine and cabergoline can decrease prolactin production. In patients with prolactinomas, medicines will usually decrease the size of the tumor even when it is large. Medicines work well for most people and are well tolerated. Bromocriptine is taken 2-3 times a day and cabergoline is long acting and used once or twice a week. Most prolactinomas respond very well to medication and women are usually able to get pregnant once their levels normalize. The medications are usually stopped during pregnancy but can be safely continued. The most common side effects are lightheadedness, nausea, and headache. Slowly increasing the dose helps with side effects. Another way to decrease the side effects is to give bromocriptine in a suppository directly in the vagina. This is an off-label use of the medicine.
Surgery: Surgery is usually done through the nose, to remove a tumor. Surgery may be used if medicines have not been effective or cause too many side effects.
Radiation: Rarely, if medicines and surgery have not been effective, radiation is used to shrink the tumor.
Hypothyroidism is treated with synthetic thyroid hormone, which should bring prolactin levels back to normal. If high prolactin levels are caused by prescription medications, other types of medications can be explored.