Subjects: patients with postoperative local recurrent or metastatic differentiated thyroid cancer .

Experimental group: Recombinant human thyroid stimulating hormone injection: 0.9mg/1.0mL/piece; intramuscular injection; once a day for two consecutive days. Control group: Thyroid hormone withdraw for 4-6 weeks.

The two groups were treated with radioiodine 131I after plasma thyroid stimulating hormone elevated (>30mU/L). The efficacy and adverse reactions were observed.

Inclusion Criteria:

• Age: 18~75 years old (including 18 and 75 years old);
• ECOG: 0-2 points;
• Expected survival of more than 3 months; Differentiated thyroid carcinoma undergoing total thyroidectomy or subtotal thyroidectomy and confirmed as locally recurrent or metastatic disease by imaging, serum tumor marker, biopsy pathology; at least one measurable lesion (diameter of the tumor ≥10 mm), and meets the requirements of RECIST 1.1.
• Hemoglobin ≥80g/L, neutrophil ≥1.5×109/L, platelet count ≥80×109/L, serum creatinine ≤1.5× upper limit of normal or creatinine clearance ≥60ml/min, Blood urea nitrogen ≤2.5× upper limit of normal (ULN); Total bilirubin ≤1.5×ULN; Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤2.5×ULN; If accompanied by liver metastasis, ALT and AST≤5×ULN albumin ≥25 g/L;
• Women of childbearing potential must have taken reliable contraceptive measures or undergone a pregnancy test (serum or urine) within 7 days prior to enrollment, with a negative result, and be willing to use appropriate contraceptive methods during the trial and for 1 year after the last dose of 131I (for women), or for 6 months after the last dose of 131I (for men);
• Participants voluntarily joined the study and signed informed consent, with good compliance and follow-up.

Exclusion Criteria:

• Patients with severe and uncontrolled diseases, including: 1) Uncontrolled hypertension (despite optimal drug therapy, systolic blood pressure ≥140mmHg or diastolic blood pressure ≥90mmHg); 2) Poorly controlled arrhythmias of ischemic heart disease or myocardial infarction of grade II or above (including corrected QT interval male ≥450 ms, female ≥470 ms) and ≥2 congestive heart failures (New York Heart Association classification); 3) Poorly controlled diabetes (fasting blood sugar >10mmol/L); 4) Active or poorly controlled severe infections (according to Common Terminology Criteria for Adverse Events ≥ grade 2); 5) Patients with active hepatitis B or hepatitis C (hepatitis B: positive HBsAg and hepatitis B virus (HBV) DNA ≥500 IU/mL; hepatitis C: positive hepatitis C virus RNA and abnormal liver function), or active infections requiring antimicrobial therapy (e.g., with antibiotics, antiviral drugs, antifungal drugs); 6) Renal insufficiency: urine routine shows urine protein ≥++ or confirmed 24-hour urine protein ≥1.0 g; 7) Patients with seizures requiring treatment.
• Received surgical treatment, incisional biopsy, or major trauma within 28 days prior to randomization;
• Unable to quit or with a history of psychiatric medication abuse;
• Allergic to the investigational drug (recombinant human thyroid stimulating hormone or 131I) or its excipients;
• Had an infection within 4 weeks prior to screening, including bacterial, viral, or fungal infections, with ongoing symptoms at the time of screening;
• Received lipophilic iodine contrast agents (such as iodized oil, iodized benzene, etc.) within the past 3 months or received water-soluble iodine contrast agents (such as iohexol, iodinated glycerol, etc.) within the past 1 month prior to screening;
• Pregnant or lactating women, or women who engaged in unprotected sexual intercourse within the two weeks prior to screening, or women with a positive blood pregnancy test at screening;
• Male subjects (or their partners) or female subjects who have plans for fertility or donation of sperm or ova during the entire study period and within 6 months after the end of the study, and who are unwilling to adopt contraceptive measures during the study period and within 6 months after the end of the study;
• Researchers believe that the presence of any condition may harm the subjects or prevent them from meeting or fulfilling the study requirements.