IGF1 and thyroid cancer: In this regard, it should be considered that a number of placental hormones (other than estrogens) and growth factors (i.e., insulin-like growth factors 1 and 2, epidermal growth factor, vascular endothelial growth factor, and members of the transforming growth factor-β superfamily) are increased within the maternal circulation throughout gestation (95) and might theoretically contribute to thyroid cancer occurrence/progression in pregnancy.