The adrenal gland is actually two endocrine organs, one wrapped around the other. The outer adrenal cortex secretes many different steroid hormones, including glucocorticoids such as cortisol, mineralocorticoids such as aldosterone, and steroids related to androgens, chiefly dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS). The glucocorticoids help regulate carbohydrate, protein, and fat metabolism. The mineralocorticoids help to regulate Na+ and K+ balance and extracellular fluid volume. The glucocorticoids and mineralocorticoids are essential for survival, but no essential role has been determined for adrenal androgens. The inner adrenal medulla, discussed in Chapter 12, secretes catecholamines (epinephrine, norepinephrine, and dopamine).
Mainly because of their potent immunosuppressive and anti-inflammatory effects, glucocorticoids are commonly used in pharmacologic doses to treat diseases such as autoimmune disorders. Interestingly, although the deleterious effects of glucocorticoids in states of hypercortisolism and the beneficial effects of their use in pharmacotherapy are well understood, the actual role of endogenous glucocorticoids in metabolic homeostasis during times of minimal stress remains somewhat enigmatic.
The major disorders of the adrenal cortex (Table 21–1) are characterized by an excessive or deficient secretion of each type of adrenocortical hormone: hypercortisolism (Cushing syndrome), adrenal insufficiency (Addison disease), hyperaldosteronism (aldosteronism), hypoaldosteronism, and androgen excess.
TABLE 21–1Principal diseases of the adrenal glands. |Favorite Table|Download (.pdf) TABLE 21–1 Principal diseases of the adrenal glands.
|Cortex Hyperfunction |
|Bilateral hyperplasia |
|ACTH excess (mainly affects zona fasciculata and zona reticularis) |
Enzyme deficiencies (with ACTH excess)
(with androgen excess and cortisol deficiency)
|ACTH-independent macronodular hyperplasia (eg, ectopic receptor expression) |
| Primary aldosteronism |
| Hypercortisolism (Cushing syndrome) |
| Hyperandrogenism (virilization) (rare) |
| Cushing syndrome |
| Virilization |
| Feminization (rare) |
|Cortex Hypofunction |
|Bilateral adrenal gland destruction (Addison disease) |
|Congenital adrenal hyperplasia (eg, 21-hydroxylase deficiency) |
|Ischemia, shock |
|Hemorrhage, anticoagulation |
|Metastatic cancer |
|Congenital (eg, cytomegalic adrenocortical hypoplasia, DAX1 mutation) |
|Medulla Hyperfunction |
|Hyperplasia (rare) |
|Other: ganglioneuroma, neuroblastoma |
|Medulla Hypofunction |
NORMAL STRUCTURE & FUNCTION OF THE ADRENAL CORTEX
The adrenal glands are paired organs located in the retroperitoneal area near the superior poles of the kidneys (Figure 21–1). They are flattened, crescent-shaped structures, which together normally weigh about 8–10 g. Each is covered by a tight fibrous capsule and surrounded by fat. The blood flow to the adrenals is copious.
Human adrenal glands. Note the location of the adrenal at the superior pole of each kidney. Adrenocortical tissue is stippled; adrenal medullary tissue is gray. Also shown (turquoise) are extra-adrenal sites at which cortical and medullary tissues are sometimes found. (Redrawn, with permission, from Forsham PH. The adrenal cortex. In: Williams RH, ed. Textbook of Endocrinology, 4th ed. Saunders, 1968. Copyright © Elsevier.)