Prolactin
Pituitary hormone that suppresses the HPG axis when elevated. Ruled out before TRT to catch reversible prolactinoma-driven hypogonadism.
TL;DR. Normal adult male: ~2-18 ng/mL. Always measured in the initial low-T workup. Mildly elevated values (15-50) are usually benign and transient, repeat before alarm. Persistent >50 or any value >100 needs pituitary MRI. Easy to cure with cabergoline; missing it means missing a reversible cause of low testosterone.
Definition
Prolactin is a 198-amino-acid polypeptide hormone secreted by lactotroph cells of the anterior pituitary. Its secretion is under tonic inhibition by hypothalamic dopamine. Anything that reduces dopamine tone, medication, pituitary stalk compression, or adenoma, raises prolactin. Persistent hyperprolactinemia suppresses GnRH pulsatility, which lowers LH and FSH and produces secondary hypogonadism.
Reference range (adult males)
| Range | Prolactin (ng/mL) | Interpretation |
|---|---|---|
| Normal | 2-18 | No action |
| Mildly elevated | 15-50 | Repeat draw; check meds |
| Moderately elevated | 50-100 | Pituitary MRI; endocrine referral |
| Highly elevated | >100 | Prolactinoma highly likely |
| >200 | >200 | Macroprolactinoma likely |
Units: ng/mL × 21.2 = mIU/L. Ranges are laboratory-dependent.
What high prolactin means
- Physiologic / transient: stress, recent exercise, nipple stimulation, recent sexual activity, sleep disruption, large meal.
- Pharmacologic: antipsychotics (risperidone, haloperidol), SSRIs, tricyclics, metoclopramide, opioids, H2 blockers, verapamil, estrogens.
- Pathologic: prolactinoma (micro <10 mm, macro ≥10 mm), other pituitary tumors via stalk compression, hypothyroidism, chronic renal failure, hepatic cirrhosis, chest-wall lesions.
- Symptoms: low libido, erectile dysfunction, infertility, galactorrhea (rare in men), headache or visual-field defect if macroadenoma.
What low prolactin means
- Dopamine-agonist therapy (cabergoline, bromocriptine), expected.
- Panhypopituitarism, rare; usually with other pituitary-hormone deficiencies.
- Isolated low prolactin in a healthy man needs no treatment.
When to test
- Baseline workup of low testosterone, before starting TRT.
- Any new galactorrhea, severe headache, or bitemporal-hemianopsia visual change.
- Workup of male infertility.
- Before starting or tapering a dopamine antagonist long-term.
Related tests
FAQ
- What is the normal prolactin range for men?
- Approximately 2-18 ng/mL for adult men. Values 15-50 are mildly elevated and usually benign (stress, recent exercise, recent sexual activity, nipple stimulation, or meds). Persistent values >50 warrant a repeat draw and pituitary MRI consideration. Values >100-200 strongly suggest prolactinoma.
- Why is prolactin tested before TRT?
- Because a prolactinoma (prolactin-secreting pituitary tumor) is a reversible cause of secondary hypogonadism. Treating the prolactinoma with a dopamine agonist (cabergoline, bromocriptine) can restore the native HPG axis and normalize testosterone without TRT. Missing this at baseline means missing a surgical or medical cure.
- What causes high prolactin?
- Physiologic (benign): stress, recent exercise, nipple stimulation, recent sexual activity, sleep disruption, large meal. Pharmacologic: antipsychotics, SSRIs, tricyclics, metoclopramide, opioids, H2 blockers, verapamil, estrogens. Pathologic: prolactinoma, other pituitary tumors (by stalk compression), hypothyroidism, chronic renal failure, hepatic cirrhosis, chest-wall lesions.
- What does low prolactin mean?
- Low prolactin rarely matters clinically in men. Causes include dopamine-agonist therapy (cabergoline, bromocriptine) and panhypopituitarism. Isolated low prolactin in an otherwise-healthy man needs no treatment.
- How should prolactin be drawn?
- Morning fasting, at rest for 15-30 minutes, at least 1 hour after waking, avoiding nipple stimulation, sexual activity, and heavy exercise that day. Repeat any mildly elevated result, physiologic surges can easily double the number transiently.