There are no science or studies to prove that PMO can lower testosterone, so NoFap should be increasing testosterone because of the absence of PMO, but maybe with a little logic, we can create theories that move us in the right direction. Prolactin is released upon orgasm and prolactin inhibits both dopamine and testosterone. Dopamine and testosterone both have a bidirectional relationship, if one goes down the other goes down and vice versa. So, if you are an addict and habitually PMO'ing without giving the body time to recover then your body is filled with prolactin which will inhibit testosterone which will inhibit dopamine, which will end up inhibiting each other which will cause who knows what because of the inhibition of testosterone which regulates a lot of things in the male body. This would probably throw the body out of whack with stress, then the vicious cycle continues. This is far as my research has brought me and the last part is a bit of conjecture, very simple probably, but perhaps there something about this and that we are abusing the male body by O'ing so often and frequently. Also, I've tested my free testosterone which has came back very low for my age, but I believe I am a severe case of this addiction, so there's that.