Context: Although the "backdoor" pathway to dihydrotestosterone has been postulated in the fetal-to-early-infantile period of patients with cytochrome P450 oxidoreductase deficiency (PORD), clinical data in support of this pathway remain limited. Objective: The objective of this study was to obtain clinical evidence for the presence of the backdoor pathway in PORD. Setting: This was a collaboration study between laboratories and hospitals. Subjects: Twenty-two Japanese patients with molecularly confirmed PORD and 1763 control subjects participated in this study. Intervention: Urine steroid profile analysis was performed by gas chromatography/mass spectrometry. In five patients and 776 control subjects, urine samples were obtained before 12 months of age. Main Outcome Measure: The main outcome measure was identification of a urine steroid(s) indicating the backdoor pathway. Results: In the PORD patients, pregnanediol, pregnanetriolone, and pregnanetriol were obviously elevated, and the urine steroid ratios reflecting CYP17A1 and CYP21A2 activities were decreased throughout the examined ages. Furthermore, etiocholanolone and 11-hydroxyandrosterone, which should originate almost exclusively from androstenedione in the conventional "frontdoor" pathway, were grossly normal or somewhat decreased since early infancy, whereas androsterone, which can be derived not only from androstenedione and dihydrotestosterone in the conventional frontdoor pathway but also from 5α-pregnane-3α, 17α-diol-20-one in the backdoor pathway, was increased during early infancy and remained grossly normal thereafter. Thus, the androsterone to etiocholanolone ratio was increased during early infancy and remained grossly normal thereafter. 5α-Pregnane-3α,17α-diol-20-one was elevated throughout the examined ages. Conclusions: The increased androsterone excretion during early infancy, as compared with the etiocholanolone and 11-hydroxyandrosterone excretions in the same period, suggests the presence of the backdoor pathway in PORD.
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