Use of the colonic potential difference as a means of assessing the efficacy of different suppressive steroid regimens was explored in a patient with incomplete 21-hydroxylase deficiency. Changes in the potential difference were found to closely reflect changes in the plasma concentration of hormones such as aldosterone, androstenedione, dehydroepiandrosterone, and dehydroepiandrosterone sulfate. Dexamethasone, which produced the most marked change in the potential difference, also produced the most suppression of the plasma steroid concentrations. It is suggested that the colonic potential difference can be used as a simple alternate means of assessing the efficacy of suppressive steroid therapy in some patients with 21-hydroxylase deficiency.
(Arch Intern Med 140:1662-1664, 1980)