Plasma renin activity in the management of congenital adrenal hyperplasia.

Fourteen children with salt losing and five children with non-salt losing congenital adrenal hyperplasia were studied. Venous samples were collected for measurement of plasma renin activity, serum 17 alpha-hydroxyprogesterone, testosterone, sodium, and creatinine. Overnight urinary sodium and creatinine excretions were measured after collection on an outpatient basis. Eight ''salt losers'' had a raised plasma renin activity despite mineralocorticoid treatment, as did one ''non-salt loser''. Six of the children in whom clinical and biochemical control was inadequate, including the ''non-salt loser'', had an increase in the dose of fludrocortisone. When the investigations were repeated one month later, a fall in plasma renin activity accompanied by a fall in 17 alpha-hydroxyprogesterone in all but one patient were found. The dose of mineralocorticoid may be as critical as the dose of glucocorticoid in the management of congenital adrenal hyperplasia, and regular determination of plasma renin activity should be made, particularly if clinical control is difficult.