Referring to the cpt® codebook in the evocative/suppression subsection, if a patient has congenital adrenal hypoplasia (cah) and testing is performed to identify if the insufficiency is due to 21 hydroxylase deficiency (insufficient stimulating hormones or inability to react to those hormones), what substances are tested for and how many times must the tests be performed?

In 21 hydroxylase deficiency, the substances that are tested are 17-hydroxyprogesterone which indicate high serum level together with urinary pregnanetriol, a metabolite of 17-hydroxyprogesterone. In addition to those, 17-ketosteroids is also perform for several times within 24-hours to confirm elevated urinary level of the substance that would indicate congenital adrenal hypoplasia.