Subclinical thyroid disease and single nucleotide polymorphisms in reproductive-age women in areas of Shanxi Province, China, where iodine exposure is excessive.

BACKGROUND AND OBJECTIVES

When iodine intake is in excess, a susceptible population that has a genetic predisposition will have an increased risk of hypothyroidism or autoimmune thyroiditis. This study evaluated the vulnerability to iodine excess and subclinical thyroid disease through screening of single nucleotide polymorphisms (SNPs) in reproductive-age women to provide evidence to be used for the prevention of subclinical thyroid disease.

METHODS AND STUDY DESIGN

In Shanxi province, four areas where a range of iodine exposures from low to high were chosen in each region, 60 women were anticipated to enrol, including 20 pregnant women, 20 lactating women, and 20 non-pregnant, non-lactating women. Genotyping was performed using whole-blood samples, and the genotypes of 21 SNPs were determined and compared among areas with different water iodine and between controls and patients with subclinical thyroid disease.

RESULTS

In total, 241 participants were enrolled. Among the 21 candidate SNPs, no difference was found among areas with various water iodine, whereas, TG (rs2252696), TSHR (rs4903957), CTLA-4 (rs231775), CAPZB (rs1472565), PDE4D (rs27178), and HLA (rs2517532) were significantly associated with various subclinical thyroid diseases; in particular, the PDE4D (rs27178), ad hoc TT allele, was associated with all examined subclinical thyroid diseases.

CONCLUSIONS

Vulnerability to subclinical thyroid diseases is influenced by the presence of gene polymorphisms. There is a need for screening of suspected genes to effectively prevent and reduce the occurrence of thyroid diseases. People with the TT allele in PDE4D (rs27178) should be made aware of an increased risk of subclinical thyroid disease.