Figure 4. Steroidogenesis of the adrenals and gonads. Adrenal and gonadal steroidogenesis starting from cholesterol and showing key steroids and intermediates of the classical and alternative pathways is illustrated. Cortisol and androgen biosynthesis are under control of hypothalamic-pituitary-adrenal (HPA) axis in a negative feedback loop. Androgen synthesis occurs via classical or aberrant and alternative pathways (i.e., backdoor pathway and 11oxC19 androgen pathway). Aberrant or alternative pathways are particularly active whenever cortisol with or without aldosterone biosynthesis is impaired and androgenic precursors accumulate proximal to enzymatic block.