i think its a bit different...hcg actually restarts your natural production of test because its mimics lh(i believe its by binding to the same receptor). your testes see it and start producing testosterone. thats why its beneficial before pct and not during. so as the exo test is wearing off you give your body a jumpstart with hcg, this is then followed by the nova and clomid does to restart production of lh and fsh, which is a positive feedback on endo test production. when your body shuts down natural test production after exo test is administered it is just an effort to maintain homeostasis. your body sees a huge amount of test and thinks that it doesnt have to produce anymore.