Which feature best differentiates secondary adrenal insufficiency from primary adrenal insufficiency?

Which feature best differentiates secondary adrenal insufficiency from primary adrenal insufficiency?

• A. Skin hyperpigmentation
• B. Elevated ACTH levels
• C. Normal aldosterone response
• D. Autoimmune destruction of adrenal cortex

Answer: (C)

The key distinction is how the mineralocorticoid (aldosterone) system behaves. In secondary adrenal insufficiency, the problem is at the pituitary/hypothalamus, so cortisol is low due to low ACTH, but the adrenal cortex’s zona glomerulosa still responds to the RAAS. That keeps aldosterone production and function essentially normal. In primary adrenal insufficiency, destruction of the adrenal cortex affects all zones, including zona glomerulosa, so aldosterone production is impaired. The result is a reduced aldosterone response with electrolyte disturbances and hypotension. So, the feature that best differentiates secondary from primary adrenal insufficiency is a normal aldosterone response. The other signs—like skin hyperpigmentation or elevated ACTH—are more characteristic of primary adrenal insufficiency, while autoimmune destruction describes its cause.

The key distinction is how the mineralocorticoid (aldosterone) system behaves. In secondary adrenal insufficiency, the problem is at the pituitary/hypothalamus, so cortisol is low due to low ACTH, but the adrenal cortex’s zona glomerulosa still responds to the RAAS. That keeps aldosterone production and function essentially normal. In primary adrenal insufficiency, destruction of the adrenal cortex affects all zones, including zona glomerulosa, so aldosterone production is impaired. The result is a reduced aldosterone response with electrolyte disturbances and hypotension.

So, the feature that best differentiates secondary from primary adrenal insufficiency is a normal aldosterone response. The other signs—like skin hyperpigmentation or elevated ACTH—are more characteristic of primary adrenal insufficiency, while autoimmune destruction describes its cause.