The Molecular Biology, Biochemistry, and Physiology of Human Steroidogenesis and Its Disorders

Steroidogenesis, the processes by which cholesterol is converted to steroid hormones, involves transport proteins, enzymes, redox partners and cofactors. Most steroidogenic enzymes are either forms of cytochrome P450 or are hydroxysteroid dehydrogenases. The P450s may be either Type 1, in mitochondria, or Type 2, in the endoplasmic reticulum; these two types differ in their electron-transfer redox partners as well as in their cellular locations. Hydroxysteroid dehydrogenases may be either shortchain dehydrogenases or aldo-keto reductases, which differ in their structures and catalytic mechanisms. Recent work has identified new enzymes, co-factors and protein modifications, and has described new pathways of steroidogenesis and new sites of steroid synthesis. Thus steroidogenesis is not confined to the adrenals and gonads, and involves more than the production of aldosterone, cortisol and sex steroids. We review the enzymes, factors and pathways of human steroidogenesis and the diseases resulting from their mutations