When you have testosterone in you does your voice deepen ?

Yes, usually.: Consider an 80y/0 male and his former 40 y/0 self. Whose voice is deeper. There has been a long lived scientific relationship between a deeper voice and testosterone.

It depends: We all have some testosterone (t) in our bodies. When boys go thru puberty, their t levels increase strikingly and their voice drops. When female bodybuilders take too much t, their voices can (irreversibly) deepen too. But for most adult men, increasing their t is unlikely to change their voice, at least if their physicians monitor their levels closely.