Kisspeptin is a recently discovered peptide made in the brain that sits at the top of the reproductive hormone cascade — it turns on GnRH, which triggers LH and FSH release from the pituitary, which in turn stimulate the gonads to produce testosterone and estrogen and drive sperm/follicle development; synthetic kisspeptin is prescribed for hypothalamic amenorrhea and used off-label to boost vitality and libido, while kisspeptin antagonists treat menopausal vasomotor symptoms.