Kisspeptin-10

What it is

Kisspeptin is the signal that sits above everything else in the reproductive axis. It acts on hypothalamic neurons to drive GnRH release, which drives LH and FSH, which drive testosterone or oestrogen. Puberty begins when kisspeptin signalling switches on, and mutations that break it cause a failure of puberty entirely.

Kisspeptin-10 is a ten amino acid fragment of the native 54 amino acid peptide, retaining the receptor activity.

The trials are better than almost anything else in this category

Imperial College London ran randomised, double-blind, placebo-controlled crossover trials of kisspeptin in men and in women with hypoactive sexual desire disorder, both published in JAMA Network Open.

In men, kisspeptin administration altered brain activity in sexual processing regions on functional MRI and increased penile tumescence compared with placebo. In women, it modulated the same brain circuitry and improved measures of sexual response.

These are properly designed academic trials with imaging endpoints, published in a mainstream journal, in the exact condition the compound is discussed for. That puts kisspeptin-10 in better evidentiary shape than most of the libido-adjacent compounds on this site.

The gap between the trial and the vial

Enormous, and it comes down to four minutes.

Kisspeptin-10 has a half-life of roughly four minutes. The trials did not inject it; they infused it intravenously over about an hour while participants were in a scanner, which is the only way to maintain a meaningful concentration.

A subcutaneous injection of a peptide that clears in four minutes produces a brief spike and nothing else. Whatever the trials demonstrated, they did not demonstrate that. The longer kisspeptin-54 has been used in reproductive medicine partly for this reason.

Practical notes

• The mechanism is the opposite of a PDE5 inhibitor. Sildenafil and tadalafil act on blood flow and require desire to already be present. Kisspeptin acts on the brain circuitry of desire itself, which is the same problem bremelanotide targets by a different route.
• It sits above the whole axis, which is a reason for caution rather than enthusiasm. Compounds that act at the top of a cascade have more downstream consequences, not fewer.
• Good trials do not license the practice. This is one of the clearer cases on the site where real randomised evidence exists and the way people actually use the compound falls entirely outside it.

Side effects and warning signs

Commonly reported

• Generally well tolerated in the published trials, with adverse events comparable to placebo
• Injection-site reactions
• Flushing
• Headache

Stop and get medical help

• Any hormone-sensitive condition, since kisspeptin sits at the top of the reproductive axis and raises LH and FSH
• Use alongside other agents acting on the HPG axis, where the combined effect has not been studied at all

Sources

1. Effects of kisspeptin on sexual brain processing and penile tumescence in men with hypoactive sexual desire disorder, randomised clinical trial, JAMA Network Open 2023trial
2. Effects of kisspeptin administration in women with hypoactive sexual desire disorder, randomised clinical trial, JAMA Network Open 2022trial

From the community

Discussion for this compound concentrates in r/Peptides and r/Testosterone.

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