What are the effects of testosterone on gays?

Same as everyone. Testosterone replacement has the same effect on men whether they are gay or straight.
Independent Actions. If you are diagnosed with low-t {hypogonadism} and submit to therapy, you should experience some or all of the following effects: * improve sexual desire and function. * increase bone mineral density. * improve mood, energy and quality of life * change body composition and improve muscle mass and strength. * improve cognitive function these effects act independently from sexual orientation.