Ripple Peptides: the reach of kisspeptin

The fading response

I expected the big kisspeptin story to be a rise in reproductive hormones. The experiment that overturned my expectation contained a fall: in women with hypothalamic amenorrhea, an initially strong LH response diminished during repeated administration. The same research subject could be described as stimulation or desensitization, depending on when the observation ended.

That reversal gives the name Ripple something solid to attach to. A disturbance travels through a responsive system; its consequences depend on the system and on time. I am far more interested in that behaviour than in a list of supposed benefits with the experimental setting rubbed away.

The essays

1. Discovery starts with melanoma experiments and follows the genetic findings that brought kisspeptin into reproductive biology.
2. Timing examines an evoked hormone pulse and the response that faded under repeated exposure.
3. IVF concentrates on a trial in women at high risk of ovarian hyperstimulation syndrome.
4. Desire spends time with brain imaging, physical arousal and the differences between those measurements.
5. Appetite and anxiety gives the experiments with unchanged outcomes room of their own.

Hormones under observation

In an early study in healthy men, kisspeptin-54 raised LH, with smaller rises in FSH and testosterone. LH is a hormone used here as a readout of reproductive signaling. That uneven pattern matters: even closely connected measurements need their own results.

The later appetite experiment makes the point especially well. In women with overweight or obesity, LH increased while measured food intake and self-rated hunger remained unchanged versus vehicle. A detectable hormonal response and an unchanged appetite fit comfortably in the same experiment. For sheer explanatory power, I put this finding near the front of the collection.