When AAS are put into a male body, the body's natural negative-feedback loops cause the body to shut down its own production of testosterone via shutdown of the hypothalamic-pituitary-gonadal axis (HPGA). This causes testicular atrophy, among other things. hCG is commonly used during and after steroid cycles to maintain and restore testicular size as well as normal testosterone production.[19]
High levels of AASs, that mimic the body's natural testosterone, trigger the hypothalamus to shut down its production of gonadotropin-releasing hormone (GnRH) from the hypothalamus. Without GnRH, the pituitary gland stops releasing luteinizing hormone (LH). LH normally travels from the pituitary via the blood stream to the testes, where it triggers the production and release of testosterone. Without LH, the testes shut down their production of testosterone.[20] In males, hCG helps restore and maintain testosterone production in the testes by mimicking LH and triggering the production and release of testosterone.
If hCG is used for too long and in too high a dose, the resulting rise in natural testosterone will eventually inhibit its own production via negative feedback on the hypothalamus and pituitary gland.
PS. I have a credible double blinded cross over study of HCG from the Journal of the American association of medicine which is titled 'Chorionic Gonadotropin in weight control'...
If anyone would want this, I am going to post a link for D/L, its a PDF...PM me its an interesting read.