Prolactin test: when to take it and what it is for

People often think of prolactin like this: it is a female hormone needed only for breastfeeding. In fact, it is measured in both women and men, and a referral can be given for a wide variety of complaints. Let's break down what this test is and how not to ruin it.

What prolactin is and what it is responsible for

Prolactin is a peptide hormone produced by cells of the anterior pituitary gland, a small gland at the base of the brain. Its main job is to signal breast tissue: to grow during pregnancy and to produce milk after childbirth. That is why levels are normally high in pregnant and breastfeeding women, and low in non-pregnant women and in men.

Prolactin receptors are also found in other organs, but how much the hormone actually works there is not yet clear. Production is restrained by dopamine from the hypothalamus, while estrogens stimulate it. Levels rise with stress, anxiety, depression, severe pain, pregnancy, and breastfeeding: nipple stimulation triggers the milk ejection reflex.

Why a prolactin test is taken

A blood prolactin test (listed on forms as PRL) shows the concentration of the hormone in a blood sample. It does not explain the cause of an abnormality, but it helps the doctor understand which further tests are needed. Most often it is ordered together with other tests.

• finding the cause of irregular or absent menstruation;
• determining the causes of infertility in women and men;
• evaluation for decreased libido and erectile dysfunction in men;
• suspected prolactinoma — a benign pituitary tumor;
• monitoring a known prolactinoma: whether treatment is working and whether the tumor has returned.

When to take prolactin and on which day of the cycle

Prolactin levels change over the course of a day. To make the result comparable, blood is usually drawn three to four hours after the person wakes up. The doctor clarifies the details of preparation.

Repeat testing is common practice. If the numbers are moderately elevated, the doctor may suggest taking the blood test again and seeing whether the abnormality persists before looking for a cause.

How to prepare for a blood prolactin test

Blood is drawn from a vein, and the whole procedure takes less than five minutes. Mild pain or a bruise at the puncture site is possible, and this usually passes quickly. The doctor may ask you not to eat or drink for several hours before the test.

Medications and vitamins affect prolactin, so any medications, including supplements, should be reported in advance. You must not stop a prescribed medication on your own. Stress, physical exertion, and even sex the day before can cause a slight rise.

What elevated and decreased prolactin mean

With high prolactin in women, ovarian function is disrupted: the cycle becomes irregular or stops, infertility appears, and nipple discharge may occur. In men, the testicles are affected — libido drops, erectile dysfunction occurs, the breasts enlarge, and hair on the face and body thins. In both sexes, milk may appear outside of pregnancy and breastfeeding. In women after menopause, usually around age 50, the set of symptoms changes.

The most common cause of elevation is prolactinoma. Other possibilities include other pituitary tumors, hypothalamic diseases, hypothyroidism, kidney disease, cirrhosis, polycystic ovary syndrome, breast trauma, and some medications. A large untreated prolactinoma presses on neighboring structures: headaches, vision changes, and deficiency of other pituitary hormones appear.

Decreased prolactin is rare. It may indicate a pituitary disorder, and in a woman after childbirth it manifests as insufficient milk — usually this is the only symptom.

When to see a doctor

Reasons for consultation include an irregular cycle, nipple discharge, infertility, decreased libido, erectile dysfunction, breast enlargement in a man, and headaches with vision changes. For these complaints, people see an endocrinologist or gynecologist, and the doctor then decides which tests are needed.

A high number by itself is not a diagnosis. A high-protein diet and some medications cause elevation, and small shifts can be due to stress and exertion. The doctor considers sex, symptoms, history, and other tests, and if a prolactinoma is suspected, may order an MRI of the pituitary.

Elevated or decreased prolactin by itself is not a reason to call an ambulance. 103 and 112 — for signs of stroke or heart attack, severe injury, or another life-threatening emergency.

My text is for reference and does not replace a doctor's consultation: specific decisions about your numbers are made by a doctor.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer