This test helps to diagnose 21-hydroxylase deficiency. Women with Non-classical Congenital Hyperplasia (NC-CAH) due to 21-hydroxylase deficiency and women with Polycystic Ovarian Syndrome (PCOS) have similar clinical presentation, with hyperandrogenism, oligomenorrhea and polycystic ovaries. As line of treatment may differ in the two conditions, it is recommended to differentiate NC-CAH from PCOS. This test helps to distinguish NC-CAH from PCOS.