Multiple or single 21-hydroxylases in congenital adrenal hyperplasia?

Abstract The objective of this study was to determine whether there is a single 21-hydroxylase in CAH ∗ that is defective or multiple different 21-hydroxylases that are involved. The activity of the 17-OH progesterone 21-hydroxylase in cortisol biosynthesis was estimated by measuring plasma 17-OH progesterone and cortisol levels simultaneously at frequent intervals throughout the day in two patients with non-saltlosing CAH and three patients with salt-losing CAH. Plasma progesterone and corticosterone concentrations were also measured on the same blood samples as an index to progesterone 21-hydroxylase activity in the corticosterone biosynthetic pathway. During periods of maximal adrenal secretory activity it was found that plasma 17-OH progesterone concentrations were markedly elevated in all patients while cortisol levels were either low normal (in non-salt-losers) or low (in salt-losers). At the same time, plasma progesterone and corticosterone concentrations were normal or elevated in both forms of CAH. Although not conclusive, these results favor the multiple enzyme theory in the pathogenesis of CAH.