For example, prior genetic association evidence has found a role for cytochrome P450-containing enzymes in autism (e.g., CYP17A1, CYP19A1 and CYP11B1).13 These enzymes are critical for the conversion of different hormones along the Δ4 pathway that lead up to testosterone (e.g., progesterone, 17α-hydroxy-progesterone and androstenedione) as well as for conversion of Δ4 steroids such as progesterone and 17α-hydroxy-progesterone toward cortisol (see Supplementary Figure 1). Here, CYP19A1 is linked to autism.