I'm no pharmacologist, so forgive me if this is a rather naive post.
But I have read studies which document that both Methylphenidate and Amphetamine have some form of testosterone-blunting effect. With Methylphenidate, this appears to be due to increased liver metabolism, whereas with Amphetamine, there appear to be multiple routes.
Funnily enough, even herbal dopamine raisers, like Scutellaria Baicalensis and Salvia Miltiorrhiza, have a suppressant effect.
I am of the opinion that all of these are due to a vasoconstrictive effect of dopamine/norepinephrine (at least to some degree).
Since the standard stimulants are regarded to have the most efficacy, I have to ask, is this effect prominent at standard therapeutic doses?
If so, could these effects be mitigated with well known testosterone-sparers, like D-Aspartic Acid and Eurycoma Longifolia?