The analysis of 17-hydroxyprogesterone (17-OHP) is 1 of the 3 analytes along with Cortisol and Androstenedione that constitutes the best screening test for Congenital Adrenal Hyperplasia (CAH), caused by either 11- or 21-hydroxylase deficiency. Analysis for 17-OHP is also useful as part of a battery of tests to evaluate females with hirsutism or infertility; both can result from adult-onset CAH.