What does the Prolactin test measure?

Why is Prolactin measured?

Prolactin is measured in the assessment of galactorrhoea, oligomenorrhoea or amenorrhoea, infertility, unexplained hypogonadism, erectile dysfunction, and suspected pituitary disease, and in the monitoring of prolactinoma. Its interpretation is complicated by two analytical phenomena that change management. Macroprolactin inflates the measured value in patients without true hyperprolactinaemia and accounts for a substantial minority of raised results, so its exclusion avoids unnecessary imaging and treatment. The high-dose hook effect operates in the opposite direction: extremely high prolactin from a large macroprolactinoma can saturate immunoassay antibodies and produce a falsely low or normal result, so a large pituitary mass with only modest prolactin elevation requires serial dilution before the tumour is assumed non-functioning.

Reference ranges

Standard reference

Non-pregnant women: approximately 4–23 ng/mL (85–500 mIU/L); men: approximately 3–15 ng/mL (65–320 mIU/L); substantially higher in pregnancy and lactation

Functional medicine optimal

Not applicable — prolactin is a diagnostic hormone measurement, not a marker with a functional optimal value; a result within the sex-appropriate reference interval is the expected finding

Units

ng/mL, mIU/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.