Prolactin is an important hormone, particularly for female reproductive health. Although it is present in men, prolactin, which is produced in the pituitary gland (attached to the base of your brain), is best known for its role in enabling women to produce breast milk.

Prolactin levels increase after a woman gives birth. In addition to its role in breast milk production, these high prolactin levels can also stop menstrual periods (and bring a decrease in sexual desire) while a woman breastfeeds. Prolactin levels typically return to normal levels when the baby is weaned and a woman is no longer breastfeeding, causing the menstrual cycle to resume.

Sometimes, however, prolactin levels are high at other times; this condition is called hyperprolactinemia. Hyperprolactinemia predominately affects women, but it can cause infertility, decreased sex drive, and bone loss in both sexes.

Fortunately, hyperprolactinemia can often be treated with medication, surgery (in the case of a tumor), or other measures. Treatment is individualized to the patient, depending on their goals, explains Amanda N. Kallen, MD, a Yale Medicine reproductive endocrinologist and infertility (REI) specialist.

“For women who are trying to get pregnant, our goal is to bring prolactin levels down, because they can interfere with the regularity of the menstrual cycle,” Dr. Kallen says. “For someone who is not trying to get pregnant, we might focus instead on getting enough estrogen, since low levels of estrogen—which can be caused by prolactinemia—can interfere with bone development and other problems.”

Dr. Kallen and her REI colleagues also work closely with physicians in the Yale Pituitary Program, a leading resource for the evaluation and management of children and adults with pituitary disease. 

Most cases of hyperprolactinemia are caused by increased prolactin secretion from the pituitary gland, which also produces many other hormones that travel throughout the body. In women, physical or psychological stress, pregnancy and, interestingly, nipple stimulation have all been found to increase prolactin levels.  

In both women and men, chronic kidney disease and hypothyroidism (when your thyroid gland does not make enough of the thyroid hormone) can also lead to elevated prolactin levels. Additionally, certain drugs and medical conditions can also make prolactin levels go up.

Other times, a growth on the pituitary gland called a prolactinoma can result in extra prolactin production. “It’s benign, just like having a mole on your skin, but it can cause the pituitary gland to make more prolactin, which can interfere with other bodily processes,” Dr. Kallen explains. 

Symptoms associated with hyperprolactinemia for women include the following: 

• Milky nipple discharge
• Milk production when not pregnant or breastfeeding
• Menstrual irregularities
• Vaginal dryness, causing painful intercourse
• Fertility problems
• Headaches and visual problems (both of these are less common) 

If the prolactin level is only a little bit elevated, there may not be any symptoms at all. Dr. Kallen stresses that prolactin levels, by nature, fluctuate. “And it can do so for various reasons, so we try to rule those out when someone comes to see us,” she explains. “For example, fasting, a hot shower and sexual activity can all make your levels go up. So, when someone has abnormal levels, we make sure it wasn’t tested just after they rolled out of bed, took a hot shower, or didn’t eat.” 

In men, symptoms may include the following:

• Erectile dysfunction
• Breast enlargement (gynecomastia)
• Decreased muscle mass and body hair

Hyperprolactinemia is usually diagnosed based on the patient’s symptoms and history, as well as a physical exam. Blood tests are ordered to detect the levels of prolactin in the blood.

“If we get an abnormal level, we may repeat the blood test to make sure there are no medication interferences going on,” Dr. Kallen says. “We might also order an MRI of the brain to see if there is a prolactinoma. The condition is not complicated to diagnose, but it may take some steps to get to the final diagnosis.” 

Your treatment will be based on the cause and severity of hyperprolactinemia. If you have high prolactin levels but no symptoms, treatment may not be needed. If your symptoms are bothersome or there is a tumor, prescription medications may be used to decrease prolactin levels.

Though it is rare, if a large pituitary growth is found to be the cause of elevated prolactin, surgery may be required to remove it. 

Yale Medicine physicians are knowledgeable in all realms of reproductive endocrinology, including disorders of prolactin secretion. We understand how various hormones work together to form a complex functional reproductive unit and that each patient presents a unique clinical scenario.

We provide necessary education to empower each patient with the knowledge to understand his or her own reproductive health. We also work closely with our colleagues in the Yale Pituitary Program if the case is particularly complex and we need additional expertise.