Glucocorticoid receptor Gene (NR3C1) Polymorphisms and Haplotypes in patients with congenital adrenal hyperplasia

Background: Lifelong glucocorticoid (GC) replacement is the mainstay treatment of congenital adrenal hyperplasia (CAH) due to classic 21-hydroxylase deficiency (21-OHD). Challenges posed by therapeutic management of these patients are well known, but novel insights into the variability in clinical response to GC highlight a role for single nucleotide polymorphisms (SNPs) of the glucocorticoid receptor gene (NR3C1).

Aim: To assess whether six commonly studied NR3C1 SNPs, which were previously associated with modified response to GC, are associated with CAH. We further assessed the linkage disequilibrium (LD) among these NR3C1 SNPs and their combination into haplotypes.

Methods: Genotypes were determined by Taqman allele discrimination assays for Tth111I (rs10052957), ER22 (rs6189), 23 EK (rs6190), N363S (rs56149945), BclI (rs41423247) and 9β (rs6198) in a Brazilian cohort of 102 unrelated 21-OHD patients and 163 unrelated healthy subjects (controls). Haplotypes were estimated using Haplo.stats, and LD among SNPs using Haploview.

Results: Heterozygous subjects for Tth111I were more frequent in 21-OHD patients (P = 0.004), while heterozygous for BclI were more frequent in controls (P = 0.049). We found a strong LD among the six NR3C1 SNPs, and four out of six common haplotypes contained the Tth111I-variant. Although we found no significant differences in overall haplotype analysis, the BclI-haplotype was less frequent among 21-OHD patients (P = 0.0180).

Conclusions: BclI-haplotype was less common and heterozygous for Tth111I were more frequent in 21-OHD patients, while heterozygous for BclI were more frequent in controls. Our novel findings may contribute to further clinical studies on the prognostic value of NR3C1 haplotypes towards individualized treatment for 21-OHD patients.