Prolactin

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Benign, or noncancerous, tumors come in all shapes and sizes. For example, adenomas are benign tumors that grow in glands, often in glands that control the human endocrine system. When adenomas form in endocrine glands, they often cause a hormonal imbalance which can have negative effects on the body’s hormonal functions. In addition, when adenomas grow in the brain, they displace brain tissue proving the old adage that there is no such thing as a benign brain tumor because the brain is within a hard shell with no room for expansion. Let’s look at pituitary adenomas, specifically prolactinomas.

Prolactin is a hormone, actually a peptide protein. Its main function is the production of breast milk in pregnant females, but it also influences the immune system and cell growth. When a woman becomes pregnant, levels of estrogen, progesterone, and prolactin rise dramatically. During pregnancy, prolactin levels may reach 10 to 20 times normal.

Elevated prolactin levels during pregnancy cause breast enlargement, cessation of menstruation, and, at the end of a pregnancy when progesterone levels drop, production of breast milk. Prolactin levels are controlled by the pituitary gland, located under the front of the brain. The gland is located between the optic nerves. Enlargement of the pituitary gland, in this case caused by a prolactinoma, can cause both hormonal changes and symptoms related to space issues caused by abnormal pituitary growth.

The symptoms of a prolactinoma depend on the patient’s age and sex. In premenopausal women, high levels of prolactin may cause infertility and infrequent (oligomenorrhea) or absent (amenorrhea) menses. This occurs because high levels of prolactin inhibit the production of other hormones like estrogen. Low estrogen levels may cause a loss of libido as well.

Less commonly, a milky nipple discharge (galactorrhea) may be present. If the tumor is very large, headache and vision changes may be present. Vision changes may occur because the tumor presses on the optic nerves that pass on both sides of it. Postmenopausal women who do not menstruate may see only the headache and vision changes. Because estrogen levels are already low in postmenopausal women, galactorrhea is rare.

In men, elevated prolactin levels may suppress testosterone levels causing infertility, decreased energy, loss of libido, and erectile dysfunction, collectively known as hypogonadism. Men may also get headaches and vision changes. Rarely, men may experience galactorrhea. If high levels of prolactin are suspected, a simple blood test for prolactin levels is done. If high levels are confirmed, brain MRI is necessary to assess tumor size. Some medications may have side effects that stimulate prolactin secretion. Included in these are some antipsychotics, antidepressants, opiates, cocaine, and antihypertensives (i.e., verapamil).

Because prolactinomas are noncancerous tumors, they are treated differently than cancerous tumors. Dopamine agonists, which are used to treat Parkinson disease, depression, and restless leg syndrome, block dopamine receptors and lower prolactin levels. They often improve symptoms as well. Lastly, if medication fails, surgery to remove the tumor can be done.

For more information go to the website of the National Institute for Diabetes and Digestive and Kidney Diseases at: https://bit.ly/3sK3KrD 

Please direct questions and comments to This email address is being protected from spambots. You need JavaScript enabled to view it. 

By Peter Galvin, MD

 

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