**Question:** In Addison's disease drug to be given is:

A. Fludrocortisone
B. Hydrocortisone
C. Dexamethasone
D. Aldosterone

**Correct Answer:** A. Fludrocortisone

**Core Concept:** Addison's disease (primary adrenal insufficiency) is a condition where the adrenal glands are unable to produce adequate amounts of cortisol and aldosterone.

**Why the Correct Answer is Right:** Fludrocortisone is a synthetic mineralocorticoid that acts as a replacement for the deficient aldosterone in Addison's disease. Aldosterone is the natural hormone produced by the zona glomerulosa of the adrenal cortex, which regulates sodium retention and potassium excretion in the kidneys. Since patients with Addison's disease lack sufficient aldosterone production, fludrocortisone is given to compensate for this deficiency and maintain electrolyte balance.

**Why Each Wrong Option is Incorrect:**

B. Hydrocortisone: Hydrocortisone is a synthetic glucocorticoid, which is different from aldosterone. It is used in situations where cortisol deficiency is present, such as in Cushing's disease or adrenal insufficiency due to bilateral adrenal hemorrhage.

C. Dexamethasone: Dexamethasone is a synthetic glucocorticoid, similar to hydrocortisone. It is used in situations where cortisol deficiency is present.

D. Aldosterone: As explained earlier, Aldosterone is the hormone responsible for regulating sodium retention and potassium excretion; however, it is the deficient hormone in Addison's disease. Therefore, aldosterone replacement is not indicated in this condition.

**Clinical Pearl:**

In Addison's disease, besides fludrocortisone, hydrocortisone, and dexamethasone are also prescribed to replace the deficient cortisol hormone. However, when addressing the primary adrenal insufficiency, fludrocortisone is the appropriate medication to replace the deficient aldosterone hormone.