Hypotension in Addison's disease is primarily due to deficiency of which adrenal hormone?

• A. Aldosterone
• B. Cortisol
• C. Adrenaline
• D. Androgens

Answer: (A)

Aldosterone deficiency is the main reason for the hypotension in Addison's disease. Aldosterone, a mineralocorticoid, promotes sodium reabsorption in the distal nephron and collecting ducts; as sodium is reabsorbed, water follows, helping to maintain extracellular fluid volume and blood pressure. When aldosterone is缺 missing, sodium and water are lost in urine (salt wasting), leading to decreased circulating volume and low blood pressure. Cortisol deficiency can weaken vascular tone somewhat, but the primary driver of the hypotension is the loss of aldosterone. Adrenaline (epinephrine) and adrenal androgens don’t directly control this volume status, so they’re not the main cause of the low blood pressure.