Kisspeptin vs PT-141: Reproductive Hormones or Melanocortin Receptors

Kisspeptin and PT-141 both appear in research on sexual desire, but they work through different systems. Kisspeptin is a hormone at the top of the reproductive axis: it stimulates the brain's GnRH neurons, which drive luteinising hormone and, in men, testosterone. PT-141, now named bremelanotide, is a melanocortin receptor agonist with no direct role in that hormone chain.

Their status is just as different. Bremelanotide is FDA-approved as Vyleesi for one narrow indication. Kisspeptin is not approved for anything, and its human evidence is a set of short academic studies.

What each one is

• Kisspeptin is a family of related peptides of different lengths. Kisspeptin-54 is the longer form used in most recent human studies; kisspeptin-10 is the shortest fragment with full activity (George 2011). Evidence for one is not automatically evidence for the other, so the studies below say which form they used. The kisspeptin-10 guide covers the fragment in more depth.

• PT-141 (bremelanotide) is a seven-amino-acid cyclic peptide. Its label describes it as a melanocortin receptor agonist that activates several receptor subtypes, of which MC1R and MC4R are the most relevant at the approved dose, and states that how it improves low sexual desire is unknown (Vyleesi label). See the bremelanotide profile and the PT-141 guide.

What the evidence shows

Bremelanotide (PT-141)

• Approved use. Vyleesi is indicated for premenopausal women with acquired, generalised hypoactive sexual desire disorder (HSDD) that is not due to another condition, the relationship or a medicine. The label states it is not indicated for postmenopausal women or for men, and not to enhance sexual performance.

• Labelled dose. 1.75 mg by subcutaneous autoinjector into the abdomen or thigh, as needed at least 45 minutes before anticipated sexual activity, with no more than one dose in 24 hours and no more than eight a month.

• Trials. The approval rests on two identical 24-week randomised, placebo-controlled trials in premenopausal women with HSDD described in the label; one is registered as NCT02333071, with 723 participants.

• Side effects in those trials. Nausea in 40% against 1.3% with placebo, flushing in 20.3%, injection-site reactions in 13.2%, headache in 11.3% and vomiting in 4.8%. Nausea was most common after the first dose, and 8% of women stopped the trials because of it.

• Blood pressure and pigmentation. Each dose transiently raised blood pressure, by up to 6 mmHg systolic and 3 mmHg diastolic, with heart rate falling by up to 5 beats per minute; values usually returned to baseline within 12 hours. Focal hyperpigmentation occurred in 1% of trial patients, and in 38% of people in a separate study who took it daily for eight days; it did not always resolve after stopping.

All of the above is from the Vyleesi prescribing information. The PT-141 dosage guide sets the label against what is sold as research PT-141.

Kisspeptin

• Kisspeptin-10 in men. Intravenous bolus doses of 0.01 to 3.0 µg/kg caused a rapid, dose-dependent rise in luteinising hormone, with the largest response at 1 µg/kg; a 22.5-hour infusion raised testosterone and luteinising hormone pulse frequency (George 2011).

• Kisspeptin-10 and oxytocin. A single 0.24 nmol/kg intravenous bolus in 12 healthy adults raised oxytocin, more in men than in women (Galbiati 2025).

• Women with HSDD. In a crossover trial, 32 premenopausal women completed a 75-minute intravenous infusion of kisspeptin-54 and of placebo while viewing erotic videos and faces in an MRI scanner. Kisspeptin changed activity in brain regions involved in sexual and attraction processing, and no adverse effects were reported (Thurston 2022).

• Men with HSDD. In a similar crossover trial, 32 men completed kisspeptin-54 and placebo infusions. Kisspeptin changed brain activity in the sexual-processing network and increased penile tumescence in response to sexual videos by up to 56% more than placebo (Mills 2023).

• Intranasal. Intranasal kisspeptin-54 raised luteinising hormone in healthy men and women and in women with hypothalamic amenorrhoea, without reported side effects (Mills 2025).

These are mechanistic studies: a single visit, a measured response over hours, and no repeated dosing. A 2025 International Consultation on Sexual Medicine review concluded that using kisspeptin or its analogues to stimulate sexual arousal is still under investigation (Rastrelli 2025).

The differences that matter

• Approval versus investigation. Bremelanotide has an approved label with a defined population and known side effects. Kisspeptin has no approved product and no study longer than a single visit in people with low desire.

• Different populations. Bremelanotide's evidence and approval are for premenopausal women. Kisspeptin's sexual-desire studies included both women and men, but each was small and short.

• Hormone effects. Kisspeptin works by moving reproductive hormones; bremelanotide does not act through that chain.

• Form matters for kisspeptin. The desire studies used kisspeptin-54. Research vials are commonly sold as kisspeptin-10, which has its own small set of studies and no study of sexual desire.

• Research-grade PT-141 is not Vyleesi. The approved product is a fixed-dose autoinjector. Lyophilised research PT-141 is a different, unregulated product, and the label's trials do not transfer to it.

Frequently asked questions

Is kisspeptin the same as PT-141?

No. Kisspeptin acts on the reproductive hormone axis; PT-141 (bremelanotide) acts on melanocortin receptors. They are unrelated peptides.

Which works better for libido, kisspeptin or PT-141?

The evidence cannot say. No study has compared them, and their evidence differs in kind: phase 3 trials and an approved label for bremelanotide in one population, short mechanistic studies for kisspeptin.

Is PT-141 approved for men?

No. The Vyleesi label states it is not indicated for men or for postmenopausal women.

Is kisspeptin FDA-approved?

No. No kisspeptin product is approved.