Congenital Adrenal Hyperplasia

Congenital adrenal hyperplasia (CAH) refers to a group of autosomal recessive disorders in which genetic enzyme deficiencies impair normal steroid synthesis. The production of cortisol in the zona fasciculata of the adrenal cortex occurs in five major enzyme-mediated steps, and deficiency in any one of these leads to CAH. The most common form is 21-hydroxylase deficiency (21-OHD), which accounts for over 90% of CAH cases. Impaired cortisol synthesis, the common feature to all forms of CAH, leads to chronic elevation of adrenocorticotropic hormone (ACTH) and overstimulation of the adrenal cortex resulting in adrenal hyperplasia. Impaired enzyme function at each step of adrenal cortisol biosynthesis leads to an increase in precursors and deficient products. This chapter will focus on CAH owing to 21-OHD, the most frequent form of CAH.