Prolactin Testing: Beyond Milk Production
Content last reviewed 2026-09-12 · Educational information — not medical advice
Quick answer
Prolactin testing investigates nipple discharge, absent periods, infertility, low-libidity-in-men, and pituitary concerns. Mild elevations follow stress, exercise, sex, and dozens of medications; persistent marked elevation demands pituitary imaging hunting prolactinomas.
What drives prolactin up (besides tumors)
Physiological: pregnancy/breastfeeding (massive), nipple stimulation, orgasm, stress of phlebotomy itself, exercise, meals, sleep (nocturnal peaks double daytime). Pharmacological: antipsychotics (risperidone potent), metoclopramide, SSRIs, estrogens, opiates — dopamine-antagonism mechanism unifying most. Pathological-non-tumor: hypothyroidism (TRH drives prolactin), chest-wall trauma, PCOS partial associations, renal failure clearance-loss.
Interpretation ladder
25-100 ng/mL: usually medication/stress/functional — recheck timed, rested, off-interfering-drugs when feasible. 100-250: prolactinoma plausible (microadenomas commonly here). >250: macroadenoma likely until imaging denies. Macroprolactinemia (inactive bound complexes) explains harmless pseudo-elevations — request macroprolactin screening when totals confuse clinical pictures.
Symptom-driven testing indications
Women: galactorrhea, amenorrhea, infertility, osteoporosis-surprising-early. Men: low libido, ED, gynecomastia (often LATE presenters — higher tumor rates at diagnosis). Both: visual-field changes/headaches suggesting mass effect, hypopituitary companions.
Treatment overview
Cabergoline/bromocriptine shrink prolactinomas chemically (surgery reserved for resistors) — dopa-agonist therapy represents pituitary medicine's great success story. Medication-caused elevations swap-regimens rather than treating. Asymptomatic micro-elevations in healthy people often merit observation over intervention.
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Frequently asked questions
Draw timing matters?
Morning after waking, rested, unstressed, fasting-preferred — sleep/stress/orgasm spikes within hours invalidate casually-obtained samples.
Will prolactinoma affect fertility?
Cabergoline restores ovulation in most women with microadenomas — paradoxically among the MOST treatable infertility causes.