Desiccated Thyroid Extract Combined With Levothyroxine for TSH Suppression Therapy in DTC

Inclusion Criteria: * Stage 1 eligibility: (1) Age ≥ 18 years；(2) Histologically proven DTC after initial surgery (± ¹³¹I)；(3) ATA recurrence risk intermediate (low-intermediate or high-intermediate) or high；(4) On L-T4 monotherapy: TSH above target despite FT4 ≥ 90 % of normal upper limit；(5) Signed informed consent and agreement to follow-up. Stage 2 eligibility: (1) Age 18-70 years (inclusive)；(2) Histologically proven DTC undergoing first-time surgery；(3) ATA recurrence risk intermediate (low-intermediate or high-intermediate) or high；(4) Signed informed consent and agreement to post-operative follow-up. Exclusion Criteria: * (1) Non-DTC histology; (2) Hyperthyroidism, toxic adenoma, or toxic nodular goiter; (3) Malabsorptive GI disorders (e.g., H.-pylori gastritis, atrophic gastritis, celiac disease) or history of gastric bypass; (4) Hypersensitivity to levothyroxine or desiccated thyroid; (5) Angina, coronary artery disease, tachyarrhythmia, osteoporosis; (6) Concurrent malignancy; (7) Pregnant, lactating, or planning pregnancy within 12 months; (8) Severe COPD, hepatic or renal insufficiency, uncontrolled hypertension or diabetes, or any condition that could bias outcome assessment; (9) Chronic use of psychotropics, systemic glucocorticoids, amiodarone, chemotherapy, iron, thionamides, PPIs, or other drugs interfering with thyroid hormone; (10) Previous exposure to levothyroxine, desiccated thyroid, or T3 preparations; (11) Participation in another clinical trial th…