**Question:** Which is NOT a clinical feature of Addison's disease:

A. Hypotension
B. Hypokalemia
C. Hyperpigmentation
D. Hypertension

**Core Concept:** Addison's disease, also known as primary adrenal insufficiency, is a condition where the adrenal glands do not produce sufficient amounts of cortisol and/or aldosterone.

**Why the Correct Answer is Right:** D. Hypertension is not a typical clinical feature of Addison's disease. In contrast, the condition is usually associated with hypotension (low blood pressure) due to reduced production of aldosterone, a mineralocorticoid hormone responsible for maintaining electrolyte balance, specifically sodium and water retention, which is essential for blood volume expansion and elevated blood pressure.

**Why Each Wrong Option is Incorrect:**

A. Hypotension: This is a correct clinical feature of Addison's disease as mentioned earlier. Reduced aldosterone production leads to inadequate sodium retention, resulting in hypotension.

B. Hypokalemia: Hypokalemia (low potassium levels) is also a correct clinical feature of Addison's disease due to the deficiency of cortisol, a hormone that promotes potassium secretion by the distal nephron. Inadequate cortisol production leads to increased potassium loss, resulting in hypokalemia.

C. Hyperpigmentation: While hyperpigmentation might be seen in some patients with Addison's disease due to increased melanin synthesis under cortisol deficiency, it is not a universal feature of the condition.

**Clinical Pearl / High-Yield Point:** Addison's disease presents a unique combination of clinical signs and symptoms, including hypotension, hypokalemia, and occasionally hyperpigmentation. A thorough clinical examination and appropriate investigations are essential to diagnose this condition accurately.