Mutations of the hexose-6-phosphate dehydrogenase gene rarely cause hyperandrogenemic polycystic ovary syndrome

Abstract

Background/aim: Hexose-6-phosphate dehydrogenase (H6PD) inactivating mutations cause cortisone reductase deficiency, which manifests with hyperandrogenism unexplained by commonly used tests and, thus, mimics polycystic ovary syndrome (PCOS). The aim of this study was to screen for mutations of H6PD gene in PCOS patients with biochemical hyperandrogenemia.

Methods: Direct DNA sequencing of the entire H6PD coding sequence was performed in 74 PCOS patients and 31 healthy controls. Results were confirmed by PCR-restriction fragment length polymorphism assay to determine the genotypic frequency of the variants.

Results: Multiple novel missense variants were detected in the study. Two exon 2 variants (acccaggc deletion proximal to the start codon and D151A) and two exon 5 variants (R453Q and P554L) were common, occurring in 23.8%, 17.1%, 35.2%, and 16.1%, respectively. There was significant linkage disequilibrium between the exon 2 and exon 5 variants. No significant differences were observed in the genotype, allele distributions, or adrenal function tests of the variants between cases and control groups. We did not detect any reported inactivating mutations in our study.

Conclusion: Although the H6PD gene is very polymorphic and missense variants are common, coding variants rarely (<1.5%) are responsible for hyperandrogenemic PCOS. We suggest that genetic studies be reserved for patients with dexamethasone-suppressible adrenal hyperandrogenism who have a discrepancy between urinary 17α-hydroxycorticoid and cortisol excretion.

Fig. 1

Direct sequencing and restriction fragment length polymorphism assay (RFLP) results for the H6PD gene. The polymorphisms were detected by direct PCR sequencing and confirmed by RFLP: (A) An eight bp (acccaggc) deletion confirmed by Ban I digestion (The 68-bp fragment is not seen because it was too low on the gel. (B) Bbs I digestion confirms the c.452 genotype a/c, which encodes the D151A missense variant. (C) The Bsg I digestion confirms the c.1358 genotype g/a, which encodes the R453Q missense variant (the 179-bp fragment is not seen because it was too low on the gel). (D) The Ban II digestion confirms the c.1661 genotype c/t, which encodes the P554L missense variant (the 53 and 6-bp fragments are not seen because they were too low on the gel). Double and single underlines locate the homozygous and heterozygous acccaggc sequences, respectively; and arrows indicate the variants.

Fig. 2

Scattergram showing lack of relationship of common H6PD gene variants to blood levels of dehydroepiandrosterone sulfate (DHEAS), an indicator of adrenal androgenic function. WT =wild-type, UTRdel+R453Q = exon 2 acccaggc deletion+exon 5 R453Q pair, D151A+P554L = SNP pair; two PCOS with both variant pairs are included in the former group. “Other” includes singletons or other combinations of the aforementioned variants or the rare variants that are designated by asterisks.