Prolactinemia: Excess Quantities of Lesser-Known Hormone Causes Broad Range of Symptoms

By Marisa Cruz, MD

So what is prolactin anyway?

Although we’re all aware that hormonal changes take place during and after pregnancy that allow women to breastfeed, most people are not familiar with the specific hormones involved and what happens when this hormonal system breaks down. Prolactin [pro-lakten] is the name of the main hormone involved in the production of breast milk, and it is made by a tiny gland called the pituitary that sits at the base of your brain. In men and non-pregnant women, the level of prolactin in your bloodstream is kept at low levels by another chemical produced by the brain called dopamine.

How would I know if my prolactin level is high?

High levels of prolactin in women who have not yet gone through menopause can cause breast enlargement, absent menstrual periods and production of breast milk. The most common cause for increased levels of prolactin (also called hyperprolactinemia [hi-per-pro-lak-ti-ne-me-a]) is pregnancy, and in pregnancy, these symptoms are entirely normal! Outside of pregnancy and breastfeeding, however, young women should generally not be skipping periods, leaking breast milk, or having problems with fertility. If you develop these symptoms, you should think about visiting your doctor to have your prolactin level checked.

In both men and postmenopausal women, the symptoms of excess prolactin are not always obvious. Men may occasionally notice breast enlargement and leakage of breast milk, but more commonly report symptoms of erectile dysfunction, reduced energy levels, reduced interest in sex, and a decrease in amounts of facial or body hair. Postmenopausal women tend to have very few symptoms related to excess prolactin itself, and so are often only diagnosed if the hyperprolactinemia is related to a growth in the pituitary gland.

What would becausing a high prolactin level ?

A prolactin level can be checked by your doctor with a simple blood test.

Small elevations in prolactin can be caused by many factors, including stress and exercise, but if your level is significantly elevated, further testing might be needed to identify the cause of the excess hormone production. Your doctor will likely begin by confirming that you do not have any medical conditions that can cause hyperprolactinemia, including kidney disease and thyroid disorders. The doctor will also review your medication list, as multiple drugs ranging from estrogens to certain psychiatric and pain medications have been linked to high prolactin levels. Certain blood levels, such as those to check your thyroid function, can be helpful.

If those initial steps are not helpful in determining the cause of your elevated prolactin levels, your primary care doctor may refer you to an endocrinologist for additional testing and treatment. The next step in evaluation is usually a pituitary MRI, which is a specialized way of taking a picture of the brain to look specifically for abnormalities in the pituitary gland. A pituitary tumor called a prolactinoma [pro-lak-ti-noma] is the most common structural problem responsible for hyperprolactinemia and is caused by unregulated growth of the pituitary cells that make prolactin. Almost all prolactinomas are benign, meaning that they are not cancerous and do not spread to other areas of the body.

Most prolactin-producing pituitary tumors are microprolactinomas, or tumors that are smaller than one centimeter in diameter. These tumors usually cause symptoms that are related only to the high levels of prolactin in the bloodstream and typically do not increase in size over time. Macroprolactinomas are prolactinproducing tumors that are larger than one centimeter in diameter, and these tumors may cause additional symptoms related to the pressure that the tumor places on the pituitary and surrounding brain structures. In particular, patients may notice headaches, loss of vision and nausea. These tumors often grow larger over time and may require more aggressive treatment.

Occasionally, pituitary tumors that do not make hormones, or that make hormones other than prolactin, can also cause hyperprolactinemia. They do so by reducing production of dopamine [do-pa-men], the chemical that normally functions to keep prolactin levels in check. If you have high prolactin levels and are diagnosed with a pituitary tumor, your endocrinologist will likely perform additional blood tests to check for abnormalities in the levels of a variety of hormones produced by the pituitary.

How are High Prolactin Levels treated?

High prolactin levels that are causing symptoms should be treated. If you are taking a medication that might cause hyperprolactinemia, your physician will likely ask you to switch to a different type of medication. Sometimes this makes all the difference. If your medication cannot be safely changed or discontinued, your endocrinologist may recommend that you be monitored and treated for the long-term side effects of excess prolactin, including weak bones and low levels of sex hormones.

High prolactin levels that are causing symptoms should be treated. If you are taking a medication that might cause hyperprolactinemia, your physician will likely ask you to switch to a different type of medication. Sometimes this makes all the difference. If your medication cannot be safely changed or discontinued, your endocrinologist may recommend that you be monitored and treated for the long-term side effects of excess prolactin, including weak bones and low levels of sex hormones.

Medications alone are effective in treating about 90 percent of patients with prolactinomas, including both small and large tumors. While those are great odds for success with just drug therapy, about one in 10 patients will continue to have symptoms related to high prolactin levels or to the size of the tumor even after treatment. These patients are usually referred to a surgeon who specializes in the removal of pituitary tumors. In a few patients with very large tumors, radiation treatment may also be recommended after surgery.

If your prolactin level returns to normal with medications, your endocrinologist will likely try to lower your dose and eventually stop treatment after one to two years. As one of the few benefits of menopause, women who stop getting their periods can usually also discontinue treatment for hyperprolactinemia.

For some patients, the prolactin level increases again when the dose of medication is reduced. Fortunately, at the low doses used to control prolactin levels, using cabergoline for multiple years does not appear to cause significant side effects. High doses of cabergoline for long periods of time have been linked to leaky heart valves, so your endocrinologist may discuss with you obtaining an ultrasound of your heart if you are taking a higher dose than the average patient with hyperprolactinemia.

What else should I know?

Women with prolactinomas can usually become pregnant and breastfeed without problems. Knowing about your plans to become pregnant is an important part of choosing the right treatment for you, however, so make sure that your endocrinologist is aware if you decide to start a family.

Dr. Marisa Cruz is an endocrine Fellow at the University of California, San Francisco. She is also serving as the Fellow-in-Training representative on the AACE Board of Directors for 2013-2014. Her current research interests include healthcare delivery systems and expanding access to endocrine subspecialty care for vulnerable populations.