Adrenal Insufficiency

Definition

Adrenal Insufficiency (AI) is a condition characterized by the inadequate production of adrenal hormones, mainly cortisol and sometimes aldosterone. It can be primary (Addison's disease) due to adrenal gland dysfunction or secondary/tertiary due to pituitary or hypothalamic disorders.

Epidemiology

• Primary AI (Addison's disease) prevalence: ~100–140 per million
• Secondary AI is more common due to pituitary disorders or long-term corticosteroid use
• Any age group can be affected, most commonly adults aged 30–50
• No significant sex predilection in primary AI; secondary AI may vary depending on underlying cause

Etiology

• Primary AI (Addison's disease): autoimmune adrenalitis (~80–90%), infections (TB, HIV, fungal), adrenal hemorrhage, metastasis
• Secondary AI: pituitary tumors, surgery, irradiation, Sheehan’s syndrome
• Tertiary AI: chronic exogenous corticosteroid therapy leading to suppression of hypothalamic-pituitary-adrenal axis

Pathophysiology

• Deficiency of cortisol → impaired stress response, hypoglycemia, fatigue
• Deficiency of aldosterone → sodium loss, hyperkalemia, hypotension
• ACTH levels elevated in primary AI; low or normal in secondary/tertiary AI
• Secondary changes: electrolyte imbalance, dehydration, cardiovascular collapse in acute AI