Read this a second time if you plan to have kids and think taking HCG beside your TRT will save your testicles. Yes, it will help with the size but that does not mean they are also producing testosterone (because they don't have to), sperm, and even if you are producing sperm - unless analyzed under a microscope the morphology may be so bad they can't do a damn thing.
It is logical to use HCG with TRT to maintain as much testicular function as possible but it guarantees nothing. How many people have impregnated a woman in the middle or end of a large blast? I know many. How many people on TRT and HCG, can't get their wife pregnant even if hump like your life depends on it when she is ovulating? Again, I know many.
Interesting topic and everyone is different. If I could do it all over again, every time I touched testosterone I would use HCG, as it doesn't seem to raise my estrogen at all. Baby making time, I would rely on the educated guys on the forum vs. the specialists in fertility who were completely useless. SERMS / HMG / HCG - all helpful, but the question
@CoolRick poses about fibrosis is something to consider. Medical literature says it is not the norm, but it can be severe or just minor.
Not arguing with anyone - something young people who plan to have a family later should read, from the older guys who have been through it. Unfortunately, back 20-30 years ago - you had to get many of the PCT / fertility medications from a doctor and most doctors, even specialists, knew next to nothing. People can get SERMS, ancillaries now through UGL's. It was not always thus.