Objective · To investigate the effect of temporary hypothyroidism state to liver function, serum lipid and blood routine in patients with differentiated thyroid cancer (DTC) prepared for radioactive iodine treatment. Methods · A total of 182 patients with DTC undergoing radical operation of thyroid cancer and radioactive iodine treatment were collected. All these patients were divided into 3 groupsage: 26 in young group (<30 years), 112 in middle-aged group (30-54 years) and 44 in elderly group (≥55 years). Indicators of liver function, blood lipids and blood routine were compared before and after operation, among groups as well. Results · Patients under hypothyroidism state had significantly elevations in ALT, AST, LDH and serum bile acid, but a nodecrease of serum bilirubin (all P<0.05). Meanwhile they had remarkable elevations in triglyceride, cholesterol, LDL and HDL (all P<0.05). In the young group before thyroid hypothyroidism treatment, the elevation of ALT, AST, LDH and serum bile acid were more significant than those of the middle-aged and elderly patients (all P<0.05). Conclusion · The temporary hypothyroidism state of differentiated thyroid cancer patients could elevate liver enzymes as well as dyslipidemia.