Prolactin

Prolactin is a pituitary hormone that stimulates milk production after childbirth. Its blood level is measured for irregular or absent periods, infertility, nipple discharge, reduced libido and erectile dysfunction, and when a pituitary disorder is suspected.

Who the test is for

• women with irregular or absent periods and women undergoing infertility investigation;
• people with milky nipple discharge outside pregnancy and breastfeeding;
• men with reduced libido, erectile dysfunction, low testosterone or breast enlargement;
• people with headaches or visual disturbances that may indicate a pituitary change;
• people being treated for prolactinoma, a benign prolactin-secreting pituitary tumour.

What prolactin is and what it shows

Prolactin is secreted by the anterior pituitary, with its secretion continually inhibited by dopamine from the brain. Levels naturally rise in pregnancy and breastfeeding. Outside these situations, raised prolactin inhibits the hormones controlling ovarian and testicular function. In women this can cause irregular or absent cycles, absent ovulation and milky breast discharge, and in men reduced libido, erectile dysfunction, low testosterone and breast enlargement.

Prolactin is secreted in bursts and has a daily rhythm: it rises during sleep, gradually falls after waking and is lowest later in the morning. Stress, physical exertion, sexual intercourse and breast stimulation temporarily raise it, making preparation more important for this test than most others.

Save with a panel

Test Prolactin is also included in these panels.

Early menopause assessment panelFSH, LH, oestradiol, progesterone, prolactin, TSHPrice of individual tests: 100.00€90.00€Details ›Fertility assessment panelTSH, oestradiol, FSH, LH, prolactin and 2Price of individual tests: 149.00€134.00€Details ›PCOS paneloestradiol, DHEA-S, FSH, LH, testosterone and 5Price of individual tests: 210.00€156.00€Details ›

All panels including Prolactin (6) ›

Preparation and sample

Prolactin is measured in venous blood. To avoid being misled by a temporary rise, follow these instructions:

• blood is collected in the morning, no earlier than 2 hours after waking;
• come rested and without rushing, and rest for 30 minutes before collection;
• avoid strenuous exercise, sexual intercourse and breast stimulation the day before and on the collection day, and schedule breast examinations or procedures after blood collection;
• fasting is not required, but avoid a large meal before collection;
• do not stop medicines yourself, but tell your doctor which you take;
• if you take biotin (for example hair and nail supplements), mention it during blood collection.

Prolactin can be raised by medicines for psychiatric conditions (antipsychotics and some antidepressants), anti-nausea medicines such as metoclopramide and domperidone, oestrogens and some opioid pain medicines.

How to interpret the result

The reference range depends on sex and method, with physiologically higher levels during pregnancy and breastfeeding; the range is printed on the report. A doctor interprets results alongside symptoms, medicines and, if necessary, other hormones.

Raised prolactin (hyperprolactinaemia)

A mildly raised result often reflects stress during blood collection or not following preparation instructions, so a doctor usually repeats it. They may also request serial prolactin: blood is collected on three occasions over two hours while you remain at rest, showing whether the rise was temporary.

If prolactin is persistently raised and pregnancy and medicines have been excluded as causes, a doctor looks for other reasons. One is an underactive thyroid, so prolactin is measured alongside TSH; others are chronic kidney or liver disease. With markedly raised levels or symptoms such as headaches and visual disturbances, a doctor refers for pituitary magnetic resonance imaging because a common cause is then prolactinoma, usually successfully treated with medicines.

Macroprolactin

Some people have a raised result without any symptoms due to macroprolactin, prolactin bound to antibodies in larger complexes. Macroprolactin remains in the blood longer and raises the measured result but has almost no activity in the body, so it causes no symptoms and requires no treatment. When results and symptoms do not match, a doctor may request an additional macroprolactin test.

Low prolactin

Low prolactin is rarely significant. It may result from prolactin-lowering medicines or, rarely, reduced pituitary function, and can make milk production difficult after childbirth.

How to arrange testing

You can have blood taken without an appointment or referral at one of our branches across Croatia (listed under Contact). Prices for all tests and panels are available in the service price list. In the investigation of infertility and irregular cycles, prolactin is often measured as part of the Fertility investigation panel, which also contains TSH, oestradiol, FSH, LH, testosterone and AMH.

Frequently asked questions

Why is prolactin measured in the morning after rest?

Prolactin rises during sleep, while stress, exertion and breast stimulation temporarily raise it. Collection in the morning, no earlier than 2 hours after waking and after 30 minutes of rest, reduces the likelihood of a falsely raised result.

What is the difference between prolactin and serial prolactin?

For prolactin, blood is collected once. For serial prolactin, it is collected on three occasions over two hours while you rest, showing whether the rise is temporary, for example due to collection-related stress, or persists throughout the procedure. The doctor still assesses results alongside medicines, physiological causes and macroprolactin. A doctor decides which test is needed.

Is raised prolactin dangerous?

A mild increase is usually temporary or due to medicines. Persistently raised prolactin needs assessment because it can disrupt cycles and fertility, and the resulting long-term sex hormone deficiency weakens bones. Whether treatment is needed depends on the cause, symptoms and effects on sex hormones, fertility and bones; some results are simply monitored without treatment. Prolactinomas are almost always benign and usually respond well to medicines.

Can prolactin be raised in men?

Yes. In men, raised prolactin lowers testosterone and can cause reduced libido, erectile dysfunction and infertility. The cause is investigated in the same way as in women, and preparation for blood collection is the same.