The nurse explains that hydrocortisone in Addison disease primarily functions to:

• A. Increase Cardiac Output
• B. Decrease the Level of Cortisol
• C. Lower the Blood Sugar Level
• D. Regulate the Excretion of Potassium and Sodium

Answer: (D)

In Addison disease, the adrenal cortex fails to produce enough aldosterone and cortisol. Hydrocortisone provides replacement of cortisol and also has mineralocorticoid activity, which is crucial for electrolyte balance. The mineralocorticoid effect promotes sodium reabsorption and potassium excretion in the distal nephron, helping to correct salt wasting, hyperkalemia, and volume depletion that come with aldosterone deficiency. That’s why its primary function in this context is regulating the excretion of potassium and sodium.

The other options don’t fit as the main action: hydrocortisone does not lower blood glucose (in fact, glucocorticoids tend to raise it), there’s no aim to decrease cortisol levels (the therapy replaces cortisol), and while improved volume status can influence cardiac output, the central, defining purpose here is electrolyte regulation through mineralocorticoid activity.