I haven't dug deep into it but the TRIIM trial ( https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6826138/ ) seemed to show promising results with a combination of rHGH, metformin, and DHEA on thymus regrowth.
I've been doing this for some time but I replaced metformin requires RX with Berberine that is safer based on my research. less risk of lactic acidosis of the liver . I found that it's hard to find a sweet spot with DHEA. Too much leads to easy bruising.
I actually prefer pregnenolone to DHEA, I've found it to be more forgiving. I agree wrt Berberine, the lactic acidosis issue turned me off metformin as well. I believe it's the reason Peter Attia stopped using it also.