Pituitary hormone — elevated prolactin suppresses LH/FSH and testosterone. Often the hidden cause of low libido or ED.
Prolactin is best known for stimulating lactation in women, but it's present in both sexes and acts on multiple tissues. Persistently elevated prolactin suppresses GnRH at the hypothalamus, which crashes LH and FSH downstream, leading to low testosterone, low libido, and erectile dysfunction.
The biggest clinical driver of elevated prolactin is a prolactinoma (benign pituitary tumor) — these are typically detected when low T workup pulls a high prolactin and the doctor orders an MRI.
Prolactin is influenced by: stress (acute spikes), sleep (peaks during sleep — draw before noon), pregnancy/lactation, chronic kidney disease, hypothyroidism (raises it), pituitary adenomas, and pharmacologic agents — D2 antagonists (antipsychotics, metoclopramide) raise it; D2 agonists (cabergoline, bromocriptine) lower it; opioids can raise it; some peptide GHRPs (GHRP-2/6) transiently raise it (ipamorelin doesn't).
When testosterone optimization isn't working and LH is suppressed without exogenous T, check prolactin. For users on GHRP-2/GHRP-6 with libido issues, switch to ipamorelin (no prolactin spike). MK-677 can elevate prolactin in some users — monitor at 8 weeks. Persistent elevation warrants pituitary MRI workup.
Upload any lab PDF and MyProtocolStack maps your values to Prolactin and 40+ other biomarkers. StackAI interprets the trend in context of your protocol.
Start tracking →Informational only — not medical advice. Reference ranges vary by lab and individual context. Work with a licensed provider to interpret your specific results.