Remember oxytocin? It's a hormone that facilitated the let-down of milk when you were nursing, and it's released with nipple stimulation. Oxytocin also stimulates contractions for the uterus (which is why any of you who had labor induced might recognize oxytocin by another name: pitocin). Outside of childbearing, oxytocin works with other sex hormones to facilitate orgasm and increase the intensity of pelvic floor muscles. Oxytocin levels have also been noted to fluctuate throughout menstrual cycles, correlating with lubrication.
This is a hormone that has lots of favorable effects on sex! There has been research in using it to enhance sexual function, but there's not a product readily available yet. Stay tuned!