IL21R and hematocrit: It should be noted that the lack of association in our study does not completely exclude the possibility of IL-21R as a candidate gene for GD because of the following three reasons: 1) The average MAF of the six SNPs is 0.271, which gives our study genetic power of about 0.8 for GD and 0.7 for HT group with an OR of homozygote 2.0, and of heterozygote 1.5, therefore studies with a larger sample size are necessary to confirm whether patients with these SNPs have more risk for development of GD.