GPR39 and migraine disorder: The associations of six SNPs identified from our previous study, including TRPM8 rs10166942, LRP1 rs1172113, DLG2 rs655484, GFRA1 rs3781545, UPP2 rs7565931, and GPR39 rs10803531, and migraine endophenotypes, including chronic migraine and allodynia were tested.