Classic congenital adrenal hyperplasia, more commonly called classic CAH, is when there is an enzyme missing in the adrenal gland, which causes the body to have the inability to make enough cortisol.

CAH is characterized by an enzyme deficiency affecting adrenal steroid hormone production. The majority of cases are due to mutations in the CYP21A2 gene, leading to 21-hydroxylase deficiency.

In CAH, the absence of a critical enzyme allows a 46,XX fetus to produce androgens, resulting in ambiguous external genitals. A CAH individual may have an oversized clitoris and fused labia.

The tumor contained mRNA for P450sec (the cholesterol side-chain cleavage enzyme) and P450c17 (17 α ... and non-suppressible adrenal rests in CAH may be hormonally indistinguishable preoperatively.