Which finding is more characteristic of primary adrenal insufficiency than secondary?

Which finding is more characteristic of primary adrenal insufficiency than secondary?

• A. Hyperkalemia due to mineralocorticoid deficiency
• B. Hypertension due to volume overload
• C. Elevated aldosterone
• D. Elevated ACTH only

Answer: (A)

The main idea is that primary adrenal insufficiency causes loss of mineralocorticoid (aldosterone) production, whereas secondary insufficiency does not. Aldosterone acts on the distal nephron to promote sodium reabsorption and potassium excretion. When the adrenal cortex is destroyed in primary disease, aldosterone falls, leading to salt wasting, hyponatremia, hypotension, and, notably, hyperkalemia from decreased potassium excretion. In contrast, secondary adrenal insufficiency stems from pituitary or hypothalamic problems that reduce cortisol (and ACTH) but leave the renin–angiotensin–aldosterone system largely intact. Since aldosterone production is preserved, potassium levels typically stay normal, and the volume and blood pressure effects differ. So hyperkalemia due to mineralocorticoid deficiency is the finding that best distinguishes primary from secondary adrenal insufficiency.

The main idea is that primary adrenal insufficiency causes loss of mineralocorticoid (aldosterone) production, whereas secondary insufficiency does not. Aldosterone acts on the distal nephron to promote sodium reabsorption and potassium excretion. When the adrenal cortex is destroyed in primary disease, aldosterone falls, leading to salt wasting, hyponatremia, hypotension, and, notably, hyperkalemia from decreased potassium excretion.

In contrast, secondary adrenal insufficiency stems from pituitary or hypothalamic problems that reduce cortisol (and ACTH) but leave the renin–angiotensin–aldosterone system largely intact. Since aldosterone production is preserved, potassium levels typically stay normal, and the volume and blood pressure effects differ.

So hyperkalemia due to mineralocorticoid deficiency is the finding that best distinguishes primary from secondary adrenal insufficiency.