Originally Posted by
rekmeyata
I don't think low T, or thyroid, or whatever medical reason causes some athletes to become sedentary. Personally I think they just simply get burned out, and some suffer joint pain from the years of sport activity and it pains too much to do whatever they may want to do. I remember when I was racing I got burned out, and I wasn't even a pro dedicating 8 to 12 hours a day 7 days a week to it! Anyway, that's my opinion based on no facts.
Neither you nor I know the reason why the person the OP was concerned about has changed behavior.
There are numerous possibilities. One could be as you suggest. Another could be a change in health status for this person. If one suffers a thyroid problem, for example, it will make very significant changes in life outlook and energy level. A health checkup is always in order with significant changes in behavior.