Synthesis of sex steroids (
). The schematic indicates the various enzymatic pathways for synthesis of different biologically active steroid metabolites of cholesterol as the starting molecule. The various pathways are regulated in different tissues by the expression of specific enzymes that catalyze the metabolic conversions in mitochondria and smooth endoplasmic reticulum. Some tissues (e.g., adrenal glands, gonadal tissues) are the primary source of some of the biologically active steroid metabolites, whereas others can be made locally in tissues such as articular cartilage when appropriately stimulated.