If you take testosterone, your pituitary will tell your testicles that there is enough testosterone, and that they can chill out, so the testicles will produce less testosterone and less sperm.

This is why anabolic steroid users can develop shrunken (atrophied) testicles.

In addition, through enzymatic equilibrium, you will also produce more estrogen (excess testosterone is converted to estrogen and vice versa), which will further decrease male reproductive ability, and in sufficient quantities will stimulate breast gland growth.

In short, administering exogenous testosterone will have counterproductive reproductive consequences.

Interesting! Thanks for the explanation.

You'd probably hit diminishing returns when testicle shrinkage starts.