All I can say is duh at the results of the study. Most doctors, who are not endocrinologists, don't understand that the the androgen cycle is a negative feedback loop. That means that if you are a heathy adult on TRT your body will compensate for the extra testosterone in your body by producing less testosterone in your gonads. Any endocrinologist worth their salt knows this. This is why you never take TRT if you are trying to have children, because TRT can make you sterile by halting testosterone production in the gonads. You need to take clomid instead of TRT if you want to get around this negative feedback cycle.