"Androstane steroids" are aliphatic polycyclic hydrocarbons characterized by a four-ring steroidal structure with a methylation at the 10- and 13-positions. An Androstene is a subset of Androstanes commonly understood to mean that the compound has at least one double bond. Commonly, unless a compound is described as a gonane, it is understood that the compound has an 18- carbon group. However, it is intended herein that 18-Nor-Androstanes are herein regarded as 16-Androstane steroids. Furthermore, all derivatives which have the structural characteristics described above are also referred to generically as Androstane steroids.
Cells of the zona fasciculata and zona reticularis lack aldosterone synthase (CYP11B2) that converts corticosterone to aldosterone, and thus these tissues produce only the weak mineralocorticoid corticosterone. However, both these zones do contain the CYP17A1 missing in zona glomerulosa and thus produce the major glucocorticoid, cortisol. Zona fasciculata and zona reticularis cells also contain CYP17A1, whose 17,20-lyase activity is responsible for producing the androgens, dehydroepiandrosterone (DHEA) and androstenedione. Thus, fasciculata and reticularis cells can make corticosteroids and the adrenal androgens, but not aldosterone.