CircRNA casein kinase 1 gamma 1 (circ‐CSNK1G1) plays carcinogenic effects in thyroid cancer by acting as miR‐149‐5p sponge and relieving the suppression of miR‐149‐5p on mitogen‐activated protein kinase 1 (MAPK1). The gene discussed is MAPK1; the disease is thyroid cancer.