i thought i read somewhere that more than 500ius a day or in one go is not advised,
Large dosages or long-term use of HCG can lead to leydig cell desensitization. However, endos often use enormous dosages of the stuff to combat secondary hypogonadism (5000IU or more).
Basically, if you're using it post-cycle and the testes have atrophied, you get very little response even at 1500IU. After about the 4th shot at that dosage I would regain my morning erections and new that my testes had recovered. That's when I stopped the HCG.