I advise my AAS patients to use small amounts of HCG (250IU to 500IU) two days each week, right from the beginning of the cycle. This serves to maintain testicular form and function...
Any more than 500IU of HCG per day causes too much aromatase activity. Some feel aromatase is actually toxic to the Leydig cells of the testes. You are then inducing primary hypogonadism (which is permanent) while treating steroid-induced secondary (hypogonadotrophic) hypogonadism (which is temporary--hopefully).
If 250IU or 500IU on two days each week isn't enough to stave off testicular atrophy, then I recommend using it more days each week (as opposed to taking larger doses). In fact, I wouldn't mind having a guy use 250IU per day ALL THROUGH the cycle. Those that have tell me they thus avoid that edgy, burned-out feeling they usually get. They also say they simply feel better each day. Subjective reports, to be sure, but they are hard not to appreciate...