Pathophysiology
Adrenal insufficiency is classified as primary or secondary.
- Primary — also known as Addison's disease (named after the British physician who described it in 1856). In the Western world, the most frequent cause is autoimmune adrenalitis.
- Secondary — pituitary/hypothalamic failure.
Because aldosterone secretion does not depend primarily on ACTH, the zona glomerulosa continues to function appropriately in secondary adrenal insufficiency; mineralocorticoid deficiency is therefore present only in primary adrenal insufficiency.
Diagnosis and Evaluation
The diagnosis of primary adrenal insufficiency is primarily made on clinical grounds, with a high index of suspicion from the history, physical, and labs.
History and Physical
Clinical manifestations: anorexia, abdominal pain, weakness, weight loss, fatigue, hypotension, salt craving, and hyperpigmentation of the skin (in primary adrenal insufficiency).
Labs
Diagnosis is confirmed by measurements of morning serum cortisol and ACTH; patients with primary adrenal insufficiency also exhibit abnormal aldosterone and renin levels. Confirmatory testing assesses the adrenal response to ACTH stimulation (the corticotropin test).
Management
- Adrenal hormonal repletion.
- Post-operative adrenal crisis — any patient who has undergone ipsilateral partial or radical nephrectomy and is undergoing contralateral renal or adrenal surgery is at risk. Obtaining old operative or pathology reports and examining cross-sectional imaging for the presence or absence of adrenal tissue are essential in this setting. In a patient with suspected post-operative adrenal crisis, consider 2 mg dexamethasone or 100 mg hydrocortisone.
Self-Test
1. Which layer of the adrenal cortex continues to function in patients with secondary adrenal insufficiency? The zona glomerulosa (aldosterone secretion does not depend primarily on ACTH).
2. List the clinical manifestations of adrenal insufficiency. Anorexia, abdominal pain, weakness, weight loss, fatigue, hypotension, salt craving, and skin hyperpigmentation (in primary adrenal insufficiency).