Kisspeptin-10

Kisspeptin-10 is the minimal active fragment of the kisspeptin family — a 10-amino-acid peptide that sits upstream of the entire reproductive hormone cascade. It binds to KISS1R (also called GPR54) in the hypothalamus and triggers a pulse of GnRH, which then drives LH and FSH from the pituitary, which finally signal the gonads to make testosterone or estrogen. In men, a single intravenous dose at 0.3 nmol/kg raises LH within minutes; in women, responsiveness varies dramatically across the menstrual cycle.

Human trials began in the mid-2000s, originally targeting fertility disorders — hypothalamic amenorrhea, hypogonadism, IVF triggering. The peptide works cleanly: it only stimulates gonadotropins if your GnRH neurons are functional. If those neurons are absent or broken (as in some forms of congenital hypogonadism), kisspeptin does nothing. This makes it a useful diagnostic tool in reproductive endocrinology, and it's being explored as a safer alternative to hCG for triggering ovulation in IVF cycles — same efficacy, virtually zero OHSS risk because the effect lasts hours instead of days.

The catch: the native peptide has a half-life measured in minutes. Plasma peptidases chew it up fast, so you need either continuous infusion or frequent dosing to maintain an effect. Research-grade analogs with D-amino-acid substitutions last longer and hit harder, but the version in most research-market vials is the wild-type decapeptide — expect short duration and high inter-individual variability.