CYP17A1 and congenital adrenal hyperplasia: CAH is a group of autosomal recessive disorders resulting in defects in one of the proteins or enzymes involved in cortisol biosynthesis: steroidogenic acute regulatory protein (StAR), P450 cholesterol side-chain cleavage enzyme (P450scc), P450 17α-hydroxylase/17,20-lyase (P450c17), P450 oxidoreductase (POR), 3β-hydroxysteroid dehydrogenase type 2 (3βHSD2), P450 21-hydroxylase (21OH or P450c21), or 11β-hydroxylase (11βOH) (Figure 3).