For example if I just want to try trt for a year and go off it…
Will your natural testosterone levels be what it was before you did trt?
For the most part, yes. Most men can take exogenous Testosterone and once stopped, have their T levels return mostly to normal. This is the basis for steroid cycles. The process can be helped through Post Cycle Therapy (PCT) drugs and doing things to help yourself along the way while on cycle (hcg to maintain testicular function, for instance).
But that said, this is for mostly normal men. Those with already existing T deficiencies do not fall in that category, so it is a wild car as far as their after T levels look. There is certainly a higher risk for those of us in that category versus the normal population.
Likely all a moot point because if you truly need TRT and go on it, it is highly unlikely you will want to come off.