The nurse notes orthostatic hypotension in a client with Addison's disease. This finding most directly reflects a deficiency in which hormone?

• A. Increased levels of androgens
• B. A decrease in cortisol release
• C. A decreased secretion of aldosterone
• D. An increase in epinephrine secretion

Answer: (C)

Orthostatic hypotension in Addison's disease most directly reflects a deficiency of aldosterone, the mineralocorticoid that regulates salt and water balance. Aldosterone promotes sodium reabsorption in the distal nephron, with water following, which maintains extracellular fluid volume and blood pressure. When aldosterone is deficient, sodium and water are wasted, reducing circulating volume. This makes standing more likely to cause a drop in blood pressure as venous return decreases. In Addison's disease, the adrenal cortex fails to produce adequate aldosterone (and cortisol), but the immediate link to orthostatic hypotension is the mineralocorticoid deficit. Other hormones don't explain this finding as directly: cortisol deficiency affects vascular tone less specifically, epinephrine would tend to raise blood pressure, and androgens don't drive this symptom.