The cellular location, substrates and products of enzymes involved in human steroidogenesis, the production of steroid hormones from cholesterol and their transformation into other steroids. The coloured areas show the major classes of steroid hormones: progestagens, mineralocorticoids, glucocorticoids, androgens and estrogens, although some classes overlap. White circles indicate changes in molecular structure compared with precursors.Image credit: David Richfield/Mikael Häggström