Understanding thyroid aging is essential for deciphering its physiological and pathological alterations, yet the causal relationship between aging and thyroid disease remains poorly characterized. We conducted a comprehensive proteomic analysis of 6109 thyroid tissues across ages 8-87 from 22 clinical centers (retrospective and prospective cohorts). Using a machine learning-based biological aging clock, we quantified accelerated aging phenotypes in pathological tissues, including benign and malignant nodules. We identified linear and non-linear age-associated proteins and pathways related to metabolism, immune response, and extracellular matrix organization remodeling, with critical transitions observed during the third, sixth, and eighth decades. Cross-species analysis of mouse and monkey tissues uncovered conserved aging markers. Intervention studies suggested that low-protein diets delay thyroid aging in mice, and therapeutic drug screening identified potential anti-tumor candidates. This study establishes the first organ-specific thyroid aging clock, linking tumorigenesis to accelerated aging, and proposing dietary interventions for thyroid longevity.