Why is the mineralocorticoid fludrocortisone given to a patient with Addison's disease?

• A. It will keep you from getting high blood sugars.
• B. Fludrocortisone helps the body retain sodium.
• C. Fludrocortisone prevents muscle cramping.
• D. It stimulates the pituitary gland to secrete ACTH.

Answer: (B)

In Addison's disease, there is a deficiency of aldosterone, a mineralocorticoid that promotes sodium reabsorption in the kidneys and potassium excretion. Fludrocortisone acts as a synthetic mineralocorticoid to replace aldosterone, so it helps the body retain sodium (and water), expand extracellular fluid volume, and raise blood pressure. It also helps lower potassium levels. This direct replacement of the missing mineralocorticoid is why fludrocortisone is used. It isn’t used to control blood sugar, prevent muscle cramps, or stimulate ACTH release.