Refractory period (sex) for treating sexual dysfunction. Sildenafil, used in the treatment of erectile dysfunction, was found in one scientific study to have caused "a decreased postejaculatory erectile refractory time (3.2 ± 0.7 vs. 6.4 ± 0.7 minutes)" in men diagnosed with premature ejaculation. It is additionally proposed that the gonadotropin inhibitory hormone (GnIH), which is considered to inhibit the hypothalamic-pituitary-gonadal axis and sexual functions causes refractoriness of the post-ejaculatory refractory period. This hypothesis also supports the increase of oxytocin and prolactin after orgasm in accordance with the previous studies. One alternative theory explains the male refractory period in terms of a peripheral
Growth hormone by the FDA. GH has been studied for use in raising livestock more efficiently in industrial agriculture and several efforts have been made to obtain governmental approval to use GH in livestock production. These uses have been controversial. In the United States, the only FDA-approved use of GH for livestock is the use of a cow-specific form of GH called bovine somatotropin for increasing milk production in dairy cows. Retailers are permitted to label containers of milk as produced with or without bovine somatotropin. The names "somatotropin" ("STH") or "somatotropic hormone" refer to the growth hormone produced naturally in animals