Early diagnosis of salt-losing congenital adrenal hyperplasia in a newborn boy.

Assays of serum 17-hydroxyprogesterone concentration may be relied upon to establish a diagnosis of congenital adrenal hyperplasia within a few hours of birth. In a male infant the concentration of 17-hydroxyprogesterone was increased in cord serum and remained elevated until glucocorticoid therapy was started on the 5th day of life. Plasma renin activity was increased only slightly in the first few days, but a striking increase on day 5, along with a gradual increase in the serum potassium concentration, confirmed that the infant had the salt-losing form of congenital adrenal hyperplasia. It was not possible to demonstrate an increased concentration of 17-hydroxyprogesterone, in amniotic fluid obtained at 30 weeks' gestation, presumably because of interference in this assay by cross-reacting steroids. Studies of the mother's serum concentration of 17-hydroxyprogesterone and cortisol during delivery did not disclose any deviation from normal.