This process is shown in the diagram below. The effects of a steroid on gene expression and protein production are very complicated and difficult to understand. Often, the protein that is produced as a result of the dimer binding to the DNA is a regulatory protein, which is responsible for activating or suppressing other genes. This causes somewhat of a chain reaction. Also, the effect a steroid has on genes is determined by the type of cell in which it is present. For these reasons, the actual effects of steroids on gene expression will not be examined in this article.
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, dehydroepiandosterone (DHEA) and androstenedione. Thus, fasciculata and reticularis cells can make corticosteroids and the adrenal androgens, but not aldosterone.