Pituitary axis
Prolactin
Anterior pituitary lactotroph hormone; tonically inhibited by dopamine.
Sample
Serum
Fasting
Not required; avoid post-prandial draw and stress.
Clinical reference range
4 to 23 ng/mL
Non-pregnant adult · Females slightly higher
Conv: 4–23 ng/mL
Biology
What it measures
Stimulates lactation; inhibits GnRH pulsatility (causing hypogonadism when chronically elevated).
Clinical use
Why we order it
Galactorrhea, amenorrhea, infertility, low libido, suspected pituitary adenoma.
Differential
Causes of abnormal values
Causes of HIGH
- ↑Prolactinoma (>200 ng/mL highly specific for macroprolactinoma)
- ↑Stalk effect from any sellar mass
- ↑Dopamine antagonists (antipsychotics, metoclopramide)
- ↑Hypothyroidism (TRH ↑)
- ↑Pregnancy / nipple stimulation
- ↑Renal failure
Pitfalls
Pre-analytic & interpretation traps
- !Hook effect: massive prolactinoma can produce falsely low prolactin via assay saturation — request 1:100 dilution if pituitary mass with 'normal' prolactin.
- !Macroprolactin (IgG-bound, biologically inactive) gives spuriously high values — confirm with PEG precipitation.
Related