HCG or Human chorionic gonadotropin, which is derived from the urine of pregnant women, is an injectable drug available commercially in the United States as well as many other countries. Pregnyl, made by Organon, and Profasi made by Serono, are FDA approved for the treatment of undescended testicles in very young boys, hypogonadism (underproduction of testosterone) and as a fertility drug used to aid in inducing ovulation in women. Among athletes, HCG is used to stimulate natural testosterone production during or after a steroid cycle which has caused natural levels to be reduced. Stopping a steroid cycle abruptly, especially when endogenous androgens are absent, can cause a rapid loss in the athlete''s newly acquired muscle. When HCG is used to stimulate natural production, a notably pronounced crash may be avoided. HCG is always packaged in 2 different vials,one with a powder and the other with a sterile solvent. These vials need to be mixed before injecting, and refrigerated should any be left for later use.