CYP17A1 and congenital adrenal hyperplasia: In 2004, a “backdoor” pathway was described with a metabolic route from 17OHP to DHT that does not involve A4 or T. In CAH, accumulating 17OHP is 5α- and 3α- reduced before being converted to androsterone by CYP17A1 with subsequent reduction and oxidation steps yielding DHT (44).