Polymorphisms of Placental Iodothyronine Deiodinase Genes in a Rural Area of Northern China with High Prevalence of Neural Tube Defects.

Introduction: We have reported that high total homocysteine (tHCY), and the coexistence of inadequate thyroid hormones in maternal serum increase the risk of fetal neural tube defects (NTDs). Placental iodothyronine deiodinases (DIOs: DIO1, DIO2, and DIO3) play a role in regulate the conversions between different forms of maternal thyroid hormones. This study hypothesized that single nucleotide polymorphisms (SNPs) in placental DIOs genes could be related to NTDs. Methods: We performed a case-control study from 2007 to 2009 that included pregnant women from Luliang, Shanxi Province, China. Nine distinct SNPs in DIOs genes were analyzed and placental samples were obtained from 83 pregnant women with NTDs fetuses and 90 pregnant women with normal fetuses. The nine SNPs were analyzed using the Cochran-Armitage test and the Fisher's exact test. Results: There were no statistically significant differences between case and control in the nine SNPs of DIOs (P>0.05). Conclusions: The results of this study suggested that SNPs of DIOs genes in placenta among pregnant women has no statistically significant difference between the two groups, suggesting that other factors might be involved in metabolism of maternal thyroid hormone provided to fetuses, such as epigenetic modification of methylation and homocysteinylation and genomic imprinting in the placenta. Further those functional studies on placenta samples are necessary.