Secondary adrenal insufficiency is most commonly due to which etiology?

• A. Adrenal hemorrhage
• B. Adrenal adenoma
• C. Autoimmune Addison's disease
• D. Pituitary or hypothalamic disease

Answer: (D)

Secondary adrenal insufficiency arises when the pituitary or hypothalamus fails to provide adequate ACTH, so the adrenal cortex isn’t sufficiently stimulated to make cortisol. This pituitary–hypothalamic disruption is the most common source of secondary AI. Since aldosterone is mainly controlled by the renin–angiotensin system and not ACTH, mineralocorticoid function is usually preserved, so hyperkalemia and severe salt-wasting are less typical than in primary adrenal failure. You may see hyponatremia and sometimes hypoglycemia due to cortisol deficiency affecting water balance and glucose metabolism. In contrast, problems involving the adrenal glands themselves—such as hemorrhage or adenoma—cause primary adrenal insufficiency, where ACTH is high and aldosterone can be affected, and autoimmune Addison’s disease is a common cause of primary rather than secondary AI.