Prolactin
The optimal range for Prolactin (Prolactin) is commonly cited as Men: 4–10 ng/mL · keeps HPG axis suppression at bay, tighter than the standard lab reference range of Men: 4–15 ng/mL · Women: 5–25 ng/mL. Pituitary hormone - elevated prolactin suppresses LH/FSH and testosterone. Often the hidden cause of low libido or ED.
How Prolactin ranges relate
The standard lab range vs the optimization-focused target. Illustrative trajectory shows what a 12-week improvement pattern looks like — not real user data.
What Prolactin Measures
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.
What Affects This Biomarker
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).
In the Context of Peptide Protocols
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.
Peptides That Commonly Move Prolactin
Conditions That Track Prolactin
Frequently Asked Questions
What does Prolactin measure?
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.
What is the optimal range for Prolactin?
The optimal range for Prolactin is commonly cited as Men: 4–10 ng/mL · keeps HPG axis suppression at bay. The standard lab reference range is Men: 4–15 ng/mL · Women: 5–25 ng/mL.
What affects Prolactin levels?
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).
Where This Fits in Your Panel
Prolactin is one marker on a fuller panel. The Peptide Blood Work Checklist lays out the complete baseline panel, what to add by protocol type, and when to retest.
See the full blood work checklist →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 →Last reviewed: June 2026
Informational only - not medical advice. Reference ranges vary by lab and individual context. Work with a licensed provider to interpret your specific results.