Bodybuilders who take steroids (often very strong androgen receptor agonists) only go bald on top, if theyre predisposed to going bald.
If you subscribe to the DHT-causes-hairloss paradigm, it would still not be DHT per se that matters, but expression/sensitivity of the androgen receptor in...
DHT is mostly a paracrine and intracrine hormone (produced inside cells and tissues, and exerting their influence there), and its endocrine function (systemic through the circulation) is considered to be very limited, especially in adulthood.
So locally inhibiting DHT production would probably...