Prolactin in men: what it is and when it is too high

Prolactin is a hormone from your pituitary gland best known for breastfeeding, but it matters in men too. When prolactin runs too high (hyperprolactinaemia), your testosterone can fall, with lower libido, erection problems or fatigue as a result. It is one of the first hormones a doctor checks when testosterone is low for no clear reason.

In most men, prolactin is not the problem. But when it is raised, it changes the whole approach.

What is prolactin?

Prolactin is a hormone made by your pituitary, a small gland at the base of your brain. In women it drives milk production. In men the role is smaller, but a high value suppresses the drive to your testicles and so lowers your testosterone.

It works through a detour. High prolactin suppresses GnRH, which lowers your LH and FSH and drags testosterone down with it (Auriemma et al., 2023).

What is a normal prolactin value in men?

In men prolactin sits broadly below 15 to 20 µg/L (about 325 to 425 mIU/L), though the upper limit varies by lab and by unit. A single mildly raised result says little, because prolactin rises briefly with stress, exercise, a meal or even the blood draw itself.

When is prolactin too high?

A doctor speaks of hyperprolactinaemia when the value is raised on repeat testing at rest. A strongly raised prolactin can point to a prolactinoma, a usually benign growth of the pituitary (Glezer and Bronstein, 2014). In men this often brings loss of libido, erection problems and sometimes infertility (Haidenberg-David et al., 2024).

Watch one pitfall: macroprolactin. This is a large, inactive form that can inflate the result without causing symptoms. A good lab can check for it before you look further.

What can raise prolactin?

The most common cause of a raised prolactin is medication. According to the Dutch Farmacotherapeutisch Kompas, certain antipsychotics, some antidepressants and anti-nausea drugs can raise prolactin, among others. An underactive thyroid, chronic kidney disease and long-term stress can also play a part.

That is why a doctor always asks about your medicines when a value is raised. Often that already explains the picture.

Which symptoms fit a high prolactin?

In men a high prolactin often brings lower libido, erection problems and sometimes reduced fertility, because your testosterone falls. Less known are breast growth (gynaecomastia) and, rarely, some milky discharge from the nipple.

With a large prolactinoma, symptoms can appear that seem unrelated to hormones, such as headache or gaps in your field of vision, because the growth presses on nearby nerves.

Picture a man of 38 with months of lower libido and a low testosterone for no clear reason. His doctor checks prolactin, and it turns out clearly raised. That shifts attention from the testicles to the pituitary.

Even so, a single raised result is not a diagnosis. The pattern across several measurements is what counts, and the symptoms overlap with other causes of a low testosterone.

What can influence your prolactin?

What can influence your value depends mostly on the cause, and the cause also decides what makes sense. If medication is behind it, your doctor can consider whether an alternative is possible. If a thyroid problem sits underneath, attention turns there. For a prolactinoma, effective medicines exist. Do not act on this yourself: the right step depends on your full picture, and that is something to discuss with your GP.

How do you get prolactin measured?

Prolactin is best drawn at rest, ideally not straight after hard exercise, sex or heavy stress, because those raise it briefly. An abnormal result is usually confirmed with a second measurement. The prolactin value often sits on broader hormone panels, such as the Hormones Man test.

See prolactin as one puzzle piece next to your other hormones. You will find more context in our overview of male sex hormones and in the pillar on male hormonal health. If your prolactin is raised on repeat testing, discuss it with your GP.

Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.

Sources

• Auriemma RS, et al. Approach to the patient with prolactinoma. J Clin Endocrinol Metab. 2023. PMID 36974474.
• Glezer A, Bronstein MD. Prolactinoma. Arq Bras Endocrinol Metabol. 2014. PMID 24830588.
• Haidenberg-David F, et al. Overview of hyperprolactinemia: general approach and reproductive health implications. Arch Med Res. 2024. PMID 39454469.