21-Deoxycortisol-d8 is a deuterated compound of 21-Deoxycortisol. 21-Deoxycortisol has a CAS number of 641-77-0. 21-Deoxycortisol is a corticosteroid metabolite of 17-hydroxyprogesterone produced in the adrenal glandvia11-hydroxylation by 11β-hydroxylase.1,2Serum levels of 21-deoxycortisol are elevated in patients with congenital adrenal hyperplasia that are heterozygous for mutations inCYP2A21, the gene encoding steroid 21-hydroxylase, and have been used as a biomarker for the detection of 21-hydroxylase deficiencies.