What level of prolactin warrants further investigation?

Sustained levels above ~500 mIU/L in men, especially with low T or visual symptoms, warrant repeat testing and possibly pituitary MRI.

Prolactin

Quick answer

What is Prolactin?

Prolactin is a pituitary hormone. In men, persistently elevated prolactin (hyperprolactinaemia) suppresses GnRH, lowering LH and ultimately testosterone. It's the marker that catches a prolactinoma — a benign pituitary tumour that's the most common pituitary cause of secondary hypogonadism.

Units:: mIU/L
Reference range:: <350 mIU/L (men)
Sample:: Venous blood (serum)

Category: Hormones
Units: mIU/L
Reference range: <350 mIU/L (men)

What does a high Prolactin result mean?

Prolactinoma, certain medications (antipsychotics, opioids), hypothyroidism, chronic stress, recent nipple stimulation. Mild elevations are often non-pathological; significant elevations warrant pituitary MRI.

What does a low Prolactin result mean?

Generally not clinically significant in men.

Why does Prolactin matter?

A prolactin reading is the cheapest way to rule out a treatable pituitary cause of low T. Skip it and you miss it.

FAQs

What level of prolactin warrants further investigation?: Sustained levels above ~500 mIU/L in men, especially with low T or visual symptoms, warrant repeat testing and possibly pituitary MRI.

References

[1]Testosterone Therapy in Men with Hypogonadism: Endocrine Society Clinical Practice GuidelineEndocrine Society / JCEM (2018)
[2]Diagnosis and Management of Male Late-Onset HypogonadismPubMed / J Clin Endocrinol Metab

Want Prolactin interpreted in the context of your full panel? Every FORM bloodwork tier covers it, with an MD walking you through the result.

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