Serum cortisol levels rise within 30 minutes of the induction of anesthesia and remain elevated for hours to days in the face of postoperative stress. Because of cortisol's critical role in the successful handling of stress, a careful clinical assessment of adrenal function is necessary before surgery. Either deficiency or excess of cortisol can adversely affect surgical outcome. The physiology and metabolism of the adrenal cortex are briefly reviewed in this chapter to help clarify the appropriate selection of tests to verify a clinical diagnosis of adrenal cortex disorder. The adrenal medulla is discussed in Chapter 30.

Human adult adrenal glands weigh 4 to 5 g each and reside in the retroperitoneal space supermedial to the kidneys. The cortex, of mesodermal origin, occupies the outer 90% of the gland. It consists of three concentric histologic zones, two of which have apparently identical function. The outermost zona glomerulosa produces aldosterone but, because it lacks 17 α-hydroxylase activity, is unable to synthesize cortisol or androgens. The middle zona fasciculate is the largest area of the adrenal cortex, and the small innermost zona reticularis encircles the medulla. These two zonae produce cortisol, androgens, and small amounts of estrogen but lack the 18-hydroxysteriod dehydrogenase required for aldosterone synthesis. Histologic evidence suggests that the zona fasciculata responds to acute adrenocorticotropic hormone (ACTH) stimulation, whereas the zona reticularis responds to prolonged stimulation.

Adrenal steroid synthesis is controlled by the hypothalamic–pituitary–adrenal (HPA) axis.