BACKGROUND: The clinical differential diagnosis of classic 21-hydroxylase deficiency (C21OHD) and cytochrome P450 oxidoreductase deficiency (PORD) is sometimes difficult, because both deficiencies can have similar phenotypes and high blood concentrations of 17α-hydroxyprogesterone (17OHP). The objective of this study was to identify biochemical markers for the differential diagnosis of C21OHD, PORD, and transient hyper 17α-hydroxyprogesteronemia (TH17OHP) in Japanese newborns. We established a 2-step biochemical differential diagnosis of C21OHD and PORD. METHODS: We recruited 29 infants with C21OHD, 9 with PORD, and 67 with TH17OHP, and 1341 control infants. All were Japanese and between 0 and 180 days old; none received glucocorticoid treatment before urine sampling. We measured urinary pregnanetriolone (Ptl), the cortisol metabolites 5α- and 5β-tetrahydrocortisone (sum of these metabolites termed THEs), and metabolites of 3 steroids, namely dehydroepiandrosterone, androstenedione (AD4), and 11β-hydroxyandrostenedione (11OHAD4) by GC-MS. RESULTS: At a cutoff of 0.020, the ratio of Ptl to THEs differentiatedC21OHDandPORDfrom TH17OHP and controls with no overlap. Among metabolites of DHEA, AD4, and 11OHAD4, only 11β-hydroxyandrosterone (11HA), a metabolite of 11OHAD4, showed no overlap between C21OHD and PORD at a cutoff of 0.35 mg/g creatinine. CONCLUSIONS: A specific cutoff for the ratio of Ptl to THEs can differentiate C21OHD and PORD from TH17OHP and controls. Additionally, the use of a specific cutoff of 11HA can distinguish between C21OHD and PORD.
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