Testosterone therapy can shrink testicles and may need prostate checks — here’s what the science actually shows.

Yes, taking extra testosterone does cause testicles to shrink because your body senses it’s getting enough and slows down its own production — and this effect reverses when you stop. As for PSA testing, the advice isn’t clear-cut: some research says doctors should check PSA levels before starting testosterone, especially for certain groups, because it’s a standard precaution. But other research suggests testosterone doesn’t raise PSA enough to raise real concern about prostate cancer, so routine testing just because someone is on therapy isn’t universally agreed upon. The key difference? One side sees it as a safety step, the other as an overreaction.