21-hydroxylase deficiency laboratory findings
Congenital adrenal hyperplasia due to 21-hydroxylase deficiency Microchapters |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2] Ahmad Al Maradni, M.D. [3]
Overview
Laboratory findings consistent with the diagnosis of 21-hydroxylase deficient congenital adrenal hyperplasia include hyponatremia, hyperkalemia, and low cortisol level.
Laboratory Findings
Salt-wasting crises in infancy
- Basic chemistries will reveal hyponatremia, with a serum Na+ typically between 105 and 125 mEq/L. Hyperkalemia in these infants can be extreme—levels of K+ above 10 mEq/L are not unusual—as can the degree of metabolic acidosis. Hypoglycemia may be present. This is termed a salt-wasting crisis and rapidly causes death if not treated.
Childhood onset (simple virilizing) CAH
- Diagnosis of simple virilizing congenital adrenal hyperplasia type is usually confirmed by discovering extreme elevations of 17-hydroxyprogesterone along with moderately high testosterone levels. A cosyntropin stimulation test may be needed in mild cases, but usually the random levels of 17OHP are high enough to confirm the diagnosis.
Late onset (nonclassical) CAH
- Diagnosis of late-onset CAH may be suspected from a high 17-hydroxyprogesterone level, but some cases are so mild that the elevation is only demonstrable after cosyntropin stimulation.