OBJECTIVETo investigate the association of polymorphisms of start codon (Fok I site) and CDX2 binding site in vitamin D receptor gene (VDR) concerned with the effect of calcium supplementation on bone mineral density (BMD) and bone turnover markers of postmenopausal women.

METHODSTwo hundreds unrelated postmenopausal women of Han ethnicity in Shanghai were randomly divided into 2 groups of 100 women: high calcium group (1000 mg element calcium and 400 units of vitamin D were given daily for 12 months) and low calcium group (300 mg element calcium and 300 units of vitamin D were given daily for 12 months). BMD and bone turnover markers were measured at baseline and 12 months after calcium supplementation. VDR gene Fok I and CDX2 polymorphisms were analyzed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and allele-specific multiplex PCR, respectively.

RESULTSOne hundred and seventy-one women completed 12-month study period. The frequency of VDR Fok I genotypes was 48.0 % for Ff, 31.0 % for FF, and 21.0 % for ff, and the frequency of CDX2 genotypes was 56.7 % for AG, 25.7% for GG, and 17.6% for AA. The frequencies distribution of Fok I and CDX2 alleles in the entire population or in two subgroups all followed the Hardy-Weinberg equilibrium. No significant difference of baseline BMD and bone turnover markers in Fok I genotypes or CDX2 genotypes was observed in the entire population or in two subgroups. Moreover, regardless of calcium supplementation given for 12 months, no significant association was found between Fok I or CDX2 polymorphisms and the endpoint values or percentage changes of any BMD and bone turnover markers in either high calcium group or low calcium group.

CONCLUSIONThere is no significant relationship between VDR gene Fok I or CDX2 polymorphisms and the effect of high or low doses calcium supplementation on BMD and bone turnover markers in Shanghai postmenopausal women of Han ethnicity.