Why might a separate mineralocorticoid be required in the management of Addison's disease?

• A. Because Addison's doesn't need mineralocorticoids
• B. Because mineralocorticoids cause hyperglycemia
• C. Because hydrocortisone provides some mineralocorticoid activity but may not be enough
• D. Because to treat hyponatremia

Answer: (C)

In primary adrenal insufficiency, you lose aldosterone as well as cortisol, so replacement needs to address both. Hydrocortisone can cover the glucocorticoid need and it has some mineralocorticoid activity, but that activity is often not enough to maintain proper sodium and potassium balance and blood pressure. Adding a separate mineralocorticoid, like fludrocortisone, helps replace aldosterone’s effects on the kidneys—promoting sodium reabsorption, potassium excretion, and fluid volume—thereby correcting hyponatremia and preventing hyperkalemia. The other options aren’t correct because mineralocorticoids are indeed needed in Addison’s, they don’t cause hyperglycemia as the primary rationale here, and the goal of mineralocorticoid replacement is more about volume and electrolyte balance than just the hyponatremia alone.