1) it bypasses the hpta and sends a signal to the testes to start making test NOW. that swells their size and makes them much more sensitive to lh once the hpta is working.
2) it causes a massive spike in endogenous test because of the aforementioned hcg/lh synonymity, and that spike is similar to taking a shot of suspension...you need to not be doing this when you aren't on clomid, for a few reasons.
now, it's interesting to note that hcg can very easily cause desensitation of the leydig cells if use to often, but actually has an opposite effect if used at higher doses less frequntly...remember, the point here isn't increase test levels, it's to increase the tetstes' ability to recieve and respond to endogenous lh when it starts occuring again.
i always start my hcg the day i start clomid...i use 5000ius the day i start the clomid, 3500ius five days later, and 1500ius five days after that