It's very well documented. HCG is generally used to address testicular atrophy and can help with increasing DHEAs levels, but it does and will increase e2 levels in the process. This is usually a very quick process and tends to cause problems with chasing the correction through AI dosage and tweaking TRT protocol. Everyone is different with response, but the effects can be experienced as low as 250iu. It used to be just part of a standard protocol, generally through a clinic, but it is not used as much anymore because it is being better understood regarding sides and necessity.
I think the only time HCG should be used is for fertility reasons and if you plan to eventually come off of TRT.