The adrenal cortex is composed of three zones with distinct endocrine functions: zona glomerulosa (produces mineralocorticoids), zona fasciculata (produces glucocorticoids), and zona reticularis (produces sex steroids). The adrenal medulla accounts for approximately 10% of the gland and is composed of chromaffin cells that secrete catecholamines. Disturbances to the hypothalamic–pituitary–adrenal axis (Figure 31–1) result in classic endocrine disorders such as Cushing’s syndrome, hyperaldosteronism, and catechol excess from pheochromocytoma (see Tables 31–1 and 31–2). The diagnosis of these disorders requires careful endocrine and radiographic evaluation.
The hypothalamic pituitary adrenal axis.
Table 31–1.24-Hour urine measurements in patients with pheochromocytoma. |Favorite Table|Download (.pdf) Table 31–1. 24-Hour urine measurements in patients with pheochromocytoma.
Norepinephrine: 10–100 μg/24 h
Epinephrine: Up to 20 μg/24 h
Normetanephrine and metanephrine: <1.5 mg/24 h
Vanillylmandelic acid (VMA): 2–9 mg/24 h
Norepinephrine: 100–200 pg/mL
Epinephrine: 30–50 pg/mL
Table 31–2.Catecholamines in urine and plasma. |Favorite Table|Download (.pdf) Table 31–2. Catecholamines in urine and plasma.
| ||Normal no. (%) ||1–2X elevated no. (%) ||>2X elevated no. (%) |
|VMA (n = 384) ||41 (11) ||86 (22) ||257 (67) |
|MN (n = 271) ||12 (5) ||33 (12) ||226 (83) |
|UFC (n = 319) ||14 (4) ||30 (10) ||275 (86) |
Adrenal “incidentalomas” represent the unsuspected adrenal mass detected on cross-sectional imaging performed for an unrelated reason, and provide the most common presentation of all adrenal masses. The NIH and American Association of Endocrinologists recommend that each incidentaloma be evaluated for metabolic function and malignant potential unless it is an obvious myelolipoma. The differential diagnosis is quite broad (Table 31–3) and includes benign adenoma, functional adrenal tumors, metastasis and benign adrenal lesions such as myelolipoma, and neurofibroma. A systematic approach is required to differentiate functional adrenal masses that warrant removal and those lesions with a significant risk of carcinoma from the more common benign nonfunctional adenoma.
Table 31–3.Differential diagnosis of adrenal incidentaloma. |Favorite Table|Download (.pdf) Table 31–3. Differential diagnosis of adrenal incidentaloma.