There were no significant differences in the distribution of genotypes and allele frequency of IGF1R, IGF-1(6093), IGF-1(1770), IGF-2(3123), IGF2R, IGF-2(3580), IGFBP-3, and insulin between the control and CPP groups (Additional file 1: Table S1). Here, INS is linked to central precocious puberty.