Two thirds of infants with CAH have a severe form with inability to produce which mineralocorticoid?

• A. Aldosterone
• B. Androgen
• C. Progesterone
• D. Cortisol

Answer: (A)

Aldosterone is the mineralocorticoid whose production is impaired in the salt-wasting form of classic congenital adrenal hyperplasia. Aldosterone normally promotes sodium reabsorption and potassium excretion in the kidneys; without it, newborns can develop hyponatremia, dehydration, and hyperkalemia. In 21-hydroxylase deficiency CAH, cortisol and aldosterone synthesis are reduced while androgen production increases, explaining the virilization and salt-wasting features. The other hormones listed—androgens, progesterone, and cortisol—are not mineralocorticoids, and cortisol deficiency is a separate issue from the mineralocorticoid deficiency described.