Keystone Peptides: the kisspeptin story
A small piece can deserve a large part in the story. Which part deserves that weight?
The missing stone
A keystone earns its place through a particular relationship to the stones around it. That is the appeal of kisspeptin for me. The finding that first convinced me of its importance was pubertal failure associated with loss of function of its receptor: a human genetic observation, accompanied by a similar phenotype in mice whose receptor gene had been disabled. There was a specific biological job to explain.
Calling it a universal reproductive switch strikes me as overreach. Even a crucial signal operates in a system with its own responsiveness and timing. The sharp decline in hormonal response during repeated kisspeptin administration makes that especially vivid. The first response and the later response can tell very different stories. This site follows that tension, from discovery to experiments that attempt to put the signal to work.
Kisspeptin and puberty
The story begins somewhere wonderfully unexpected: a metastasis-suppressor gene studied using human melanoma cells and nude mice. The reproductive role emerged later through families with disrupted GPR54 receptor function. I enjoy the untidy history, with each experiment redirecting the questions.
The discovery history follows the cancer experiment, the puberty genetics and the later finding of a receptor that responded for longer in a girl with early puberty. The last detail matters: the story involves both lost signaling and prolonged signaling.
Hormonal timing and IVF
An experiment in women with hypothalamic amenorrhea restored pulses of LH, a reproductive hormone. A separate IVF trial studied egg maturation in women at high risk of ovarian hyperstimulation syndrome. These are different clinical questions, even though both concern reproductive signaling.
I give the IVF work particular weight because it asks for a concrete event: egg maturation in a defined treatment setting. The IVF report stays with that event and the trial's carefully bounded safety finding. The piece on rhythm takes the opposite perspective, following the responses that weaken and asking how that changes the appeal of sustained stimulation.
Desire, anxiety and appetite
Kisspeptin also enters a more elusive territory. A trial in men with hypoactive sexual desire disorder measured changes in sexual brain processing, physical arousal and reported desire. Another trial raised reproductive hormones without significantly changing anxiety. In women with overweight or obesity, hunger and measured food intake were unchanged despite an LH response.
A string of positive findings would make a less interesting story to my mind. A signal can be biologically active while leaving a particular experience unchanged. The essay on desire and mood puts those findings beside each other. For the sources themselves, there is a reading list, with the discovery papers alongside the human experiments.