I'm fat, with high blood pressure, due to sleep apnea, and the doctor says to run or do bike for 30 mins to an hour daily and not lift weights and eat less (do some diet).

The problem is that I read that things like running (or biking), for that amount of time, lowers testosterone.

Is there some exercise which doesn't lower testosterone and at the same time it's not lifting weights? Does running/biking for an hour lowers it? Does it cause some kind of permanent damage?

Once I get to an optimal weight and have my sleep problems solved, and I can lift weights, is there some amount of running or similar exercise that can be done without affecting testosterone?

Update: Thanks for the advice! I think that I'll do < 1 hour per day of cardio, that seems the best for now, and will start lifting again once I'm lose enough weight. It looks testosterone problems (and problems with other hormones) starts when one trains too much and start damaging the body.