If your gonna be on a few cycles a year every year and your young and may want some kids in future then it's a defo chap.

Most people will tell you it is not needed.

my understanding of it is that it sends contradictory signals to your HTPA. basically it functions as leutenizing hormone, which is released from your pituitary gland in response to GnRH release from the hypothalamus, which stimulates your testicles (leydig cells specifically) to produce sperm and (I think) is responsible for their maturation. normally, exogenous androgens would have your LH levels (among other things) suppressed however with HCG, this suppression (in terms of LH) does not occur, LH levels are perceived to be high, which further suppresses you, yet at the same time, the cells responsible for sperm production do not experience the suppression due to the actions of HCG. so its kinda of opposite signals. I haven't really looked into it too much, I understand the basics (theres a lot of guys here that will give you much more informative answers than I just did).