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.
The zona fasciculata chiefly produces glucocorticoids (mainly cortisol in the human), which regulates the metabolism of glucose, especially in times of stress (., part of the fight-or-flight response ), it is stimulated by the hormone Adrenocorticotropic Hormone (ACTH) which is released from the anterior portion of the pituitary and axised upon this adrenal gland. This tissue also generates a small amount of weak androgens (., dehydroepiandrosterone ). The main source of androgens will come from the zona reticularis region. In certain animals such as rodents , the lack of 17alpha-hydroxylase results in the synthesis of corticosterone instead of cortisol.