Will gym cause accelerated hair loss?

I’d strongly caution you against looking at mpb based on level of testosterone or even DHT. Mpb is a result of complex biological interactions and exercise results in complex effects on the body. Exercise association to Mpb need not have any relationship to whether or not exercise affects testosterone.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5500728/ This was published just over 2 years ago to look at the association of AGA and exercise. They got somewhat mixed results and fail to properly control for the effects of balding on degree of exercise, but nonetheless among those with a family history of AGA it does suggest at least some association of having AGA and engaging in more exercise than those without AGA. The association may be severely reduced in those without a predisposition for AGA as shown in the no family history of AGA. (Fig. 1) Which could suggest some interaction of exercise to AGA among people predisposed to AGA that is not present it those who are not predisposed to AGA.

There aren’t really worthwhile studies to answer the question since the few that exist fail to remove the issue of degree of balding affecting degree of exercise. It would probably be worthwhile to make a well designed questionnaire which effectively addresses this question, since previous studies have all been poorly designed in that regard such that we have no real evidence to answer the question of this post for causation.