Prolactin
Also written as: PRL
The milk-production hormone, which also responds readily to stress, sleep, and many common medications.
What it measures
The level of prolactin, a pituitary hormone best known for enabling milk production after childbirth. It is present in everyone, and it rises readily with stress, sleep, eating, exercise, and nipple or chest wall stimulation.
Why a doctor orders it
Ordered for irregular or absent periods, unexpected milky nipple discharge, fertility problems, low libido, or low testosterone, since high prolactin can quiet the reproductive hormone system. Also checked when a pituitary gland problem is being considered.
What is generally associated with a higher result
Broadly associated with prolactin-producing pituitary growths, but far more often with ordinary causes - stress, recent sleep, a recent meal, exercise, nipple stimulation, pregnancy, breastfeeding, and a long list of common medications. Laboratories can also detect macroprolactin, an inactive clumped form that inflates the number without any biological effect.
What is generally associated with a lower result
Low values are generally not pursued.
Everyday things that move this number
Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:
- Stress, including the stress of the blood draw itself
- Recent sleep, exercise, a meal, or breast stimulation before the draw
- Many common medications, including some used for nausea, depression, and mental health
- Pregnancy and breastfeeding
- Macroprolactin, a harmless lab finding that inflates the result
Questions to take to your appointment
- Could a medication I take be raising this?
- Should the lab check for macroprolactin before anything else is done?
- Would a sample drawn rested, and before eating, give a truer picture?
Build a printable questionnaire with your own results →
Where to read more
MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .
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