Kisspeptin

Kisspeptin is the hormone your brain uses to start the whole chain of events that leads to the production of sex hormones. Without it, the reproductive system doesn't activate. It sits right at the top of the hormonal axis — in the hypothalamus — where it triggers the release of GnRH, which in turn drives LH and FSH, which in turn tell the ovaries and testes to produce oestrogen and testosterone. Think of it as the on-switch for the entire reproductive endocrine system.

It was actually discovered twice. In 1996 it was identified as a suppressor of cancer metastasis in melanoma — at the time it was called metastin — and that's still reflected in the gene name, KISS1. Its role in reproduction wasn't recognised until the early 2000s, when researchers found that people with mutations in the kisspeptin receptor (KISS1R) fail to go through puberty. That finding opened up an entirely new understanding of how the brain controls fertility.

The main clinical interest now is in two areas. The first is fertility medicine — kisspeptin-54 is being investigated as a safer alternative to hCG for triggering egg maturation during IVF, with the advantage of a much lower risk of ovarian hyperstimulation syndrome. The second is sexual function — clinical trials at Imperial College London have shown that kisspeptin injections improve sexual desire and attraction-related brain activity in both men and women with low libido.

A 2025 study published in Lancet eBioMedicine demonstrated that an intranasal spray formulation of kisspeptin-54 can reliably raise LH levels in healthy adults and in women with hypothalamic amenorrhea, which is significant because it opens up a non-injectable route of administration. No consumer product exists — all current use is within clinical trials.