Congenital adrenal hyperplasia (CAH) is a group of inherited disorders of cortisol biosynthesis in the adrenal cortex. 21-Hydroxylase deficiency (21-OHD) is the most common form of CAH. 21-OHD is further divided into classical and non-classical forms. Nearly 25% of classical CAH patients have the simple virilizing type of CAH (SV-CAH). The incomplete loss of 21-hydroxylase activity allows it to produce enough aldosterone to avoid salt wasting, but not enough cortisol to maintain effective negative feedback on ACTH production. Alterations in adrenal hormone synthesis driven by excess ACTH results in early androgen excess causing virilization symptoms in females both in utero and later in life. SV-CAH patients need lifelong hormone replacement therapy and close monitoring for not only endocrine but also numerous other health related problems.