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

The global incidence of Differentiated Thyroid Cancer (DTC) is rising. While surgery followed by TSH suppression is the standard of care, achieving target TSH levels with levothyroxine (L-T4) monotherapy remains challenging, with only 25-70% of intermediate/high-risk patients attaining it within 6-8 months. This therapeutic dilemma stems from three key issues: impaired T4-to-T3 conversion due to DIO2 polymorphisms, the non-physiological hormone ratio of T4 monotherapy, and L-T4's narrow therapeutic window. This often results in an "under- versus over-suppression" paradox, increasing risks of recurrence, atrial fibrillation, and osteoporosis. Combining L-T4 with desiccated thyroid extract (DTE; T4:T3 ≈ 4:1) may overcome these limitations by bypassing DIO2 defects and providing a more physiological hormone profile, thereby potentially improving TSH control while mitigating side effects. Supported by the 2023 Chinese guidelines and our promising pilot data (82% cumulative target attainment at a median of 1.4 months), we propose a two-stage national study: a multicenter cohort study followed by a randomized trial, to generate high-level evidence for this combination therapy in high-risk DTC.