What is the most common hormonal deficiency in congenital adrenal hyperplasia?

Congenital adrenal hyperplasia (CAH) refers to a group of inherited disorders affecting adrenal steroidogenesis. The most common form of CAH is indeed caused by a deficiency in the enzyme 21-hydroxylase. This enzyme plays a crucial role in the synthesis of cortisol and aldosterone, two vital hormones produced by the adrenal glands. Specifically, 21-hydroxylase catalyzes the conversion of 17-hydroxyprogesterone to 11-deoxycortisol in the pathway leading to cortisol production and the conversion of pregnenolone to progesterone for aldosterone synthesis.

In the absence of adequate 21-hydroxylase activity, the pathway is disrupted, leading to decreased cortisol and aldosterone levels. This results in accumulation of steroid precursors, such as 17-hydroxyprogesterone, which can be converted into androgenic steroids, leading to virilization effects, especially in females.

Deficiencies in other enzymes, such as 17-hydroxylase, 11-hydroxylase, and 3-beta-hydroxysteroid dehydrogenase do exist but are less common. Each of these deficiencies affects different aspects of steroid hormone synthesis and presents with distinct