Background: Bi-allelic mutations of CYP21A2 encoding 21-hydroxylase are the most frequent cause of congenital adrenal hyperplasia (CAH). Non-classical CAH (NCCAH) or even just hyperandrogenism may be caused by mild or mono-allelic (single) heterozygous mutations of CYP21A2. These mutations are associated either with elevated basal or ACTH-stimulated levels of 17-hydroxyprogesterone (17OHP) in blood.
Objective and hypotheses: The objective of this study was to identify the most suitable design of 17OHP measurements and determination of 17OHP cut-off levels in order to identify patients with NCCAH.
Method: Between July 2006 and July 2015 ACTH-tests were conducted in 768 children and adolescents suspected to have NCCAH. Inclusion criteria were premature pubarche with accelerated bone age, hyperandrogenemia, hirsutism, or menstrual irregularities. 17OHP in blood was measured before, 30, and 60 after injection of 250 μg ACTH. The sum (sum17OHP), difference (diff.17OHP) and quotient (ratio17OHP) of 17OHP60, and basal 17OHP levels were monitored. Receiver operating characteristics (ROC) were plotted for the six test algorithms and the area under the curve (AUC) calculated for each. From genomic blood DNA of 371 of the subjects CYP21A2 was analyzed by DNA-sequencing and MLPA.
Results: Molecular analysis revealed mutations in 88 (23.7%) of the 371 patients. 10 of them carried bi-allelic, i.e. compound heterozygous (6) or homozygous (4) mutations. The most common mutations were p.Val281Leu (30) and p.Gln318Stop (14). Among the six tested algorithms, diff.17OHP was the best, i.e. revealing the highest AUC with respect to identifying patients with single (0.762) or bi-allelic (0.920) mutations. A diff.17OHP cut-off of >3.4 μg/l showed best combined sensitivity and specificity for identification of mutation carriers.
Conclusion: Not only bi-allelic but also heterozygous mutations of CYP21A2 can be associated with clinical signs. Our results suggest genotyping of CYP21A2 in patients with values exceeding 3.4 μg/l diff.17OHP. Bi-allelic mutations, i.e. CAH or NCCAH are associated with diff.17OHP>10 μg/l.
10 - 12 Sep 2016
European Society for Paediatric Endocrinology