IGF1 and thyroid cancer: Multivariate analysis demonstrated that serum 25(OH)D (OR=0.578, 95%CI= 0.426-0.783), IGF-1 (OR=1.019, 95%CI= 1.010-1.029) and PDGF (OR=1.007, 95%CI= 1.004-1.009) were considered independent risk factors for thyroid cancer (P<0.001, for all).