Prolactin

Prolactin is produced by the anterior pituitary gland. Its primary physiological role is initiating and maintaining lactation, but it also influences reproductive function — high prolactin suppresses gonadotropin secretion and causes irregular periods or low libido. Prolactin secretion is under continuous inhibition by dopamine from the hypothalamus; anything that interrupts this inhibition (dopamine antagonist medications, pituitary stalk compression) raises prolactin. Pregnancy, lactation and stress (including the venepuncture itself) raise it physiologically.

• Men: about 2-18 ng/mL.
• Women (not pregnant): about 2-29 ng/mL.
• Rises sharply in pregnancy and breastfeeding, and briefly with stress, sleep and the blood draw itself - so a mildly high result is often repeated.

Your lab's printed range is what counts.

• Prolactinoma — pituitary adenoma producing prolactin; values commonly >200 ng/mL.
• Medication effect — antipsychotics (risperidone, haloperidol), metoclopramide, opiates, oestrogens, some antidepressants.
• Pregnancy and lactation — physiological.
• Hypothyroidism — TRH stimulates prolactin too.
• Polycystic ovary syndrome — modest elevation common.
• Macroprolactinaemia — biologically inactive complex measured by routine assay; benign.
• Stress, recent breast exam, vigorous exercise — transient.

• Generally not clinically actionable in non-lactating individuals.
• Postpartum lactation failure — can suggest Sheehan's syndrome.
• Hypopituitarism — broader pituitary failure.

• High prolactin in women: irregular or absent periods, milky nipple discharge, low libido and difficulty conceiving.
• In men: low libido, erectile difficulty and, rarely, breast tenderness.
• A large pituitary tumour can add headaches or visual changes. Low prolactin usually causes no symptoms.