I am happy to see that hCG was one of the first discussion points. Oftentimes the quintessential concern is centered on peripheral side effects (i.e. - gyno, hair loss, lipids, blood pressure, et al...) at the expense of the most serious central side effect, hypothalamic-pituitary-dysfunction. hCG does play quintessential role here as the most tried and true (not the only). To answer your questions...
The two prototypical regimens I might employ therapeutically are one with low dose (as little as 300-500 IU daily) used throughout the cycle and/or higher dose (1000-as much as 5000 IU three times per week) if simply initiated in PCT. I would continue hCG in the case of the low-dose peri-cycle protcol; especially for the guy who still wants children. Even with on-cycle use; we have noted an average decline in sperm count that approaches literature values still at 22 months in some people (the subfertile state thought to be direct result in attenuation of testosterone). Still, there are dose- and time-dependency factors that will come into play here as well.
Again, some may not like my sperm count offering as they may certainly not care about fertility status, but it is a reflective number to approximate how long the HPGA may remain compromised, and given the dearth of research alloted in this subject area, it is the way we can translate that which has, in fact, been looked at.
Yes; dependent upon duration of the cycle and relative HPGA dysfunction (as alluded to above). There is negative feedback at the level of the hypothalamus to shut down GnRH and subsequently LH (and FSH), which will be inherently dependent upon the degree of shutdown. If you look at doses and ways used (daily versus three times per week); this focuses on how to best bring back the HPGA in my experience over the last few years with select patients and likely reflects the doses able to best keep negative feedback at bay.
D_
