Bidirectional Regulation of Urinary Stone Composition by Hypothyroidism: A Propensity Score-Matched Analysis of 33,579 Patients

Background Urolithiasis affects 14.8% of the global population, with its pathogenesis involving multiple systemic factors. Among patients with thyroid disorders, which affect 5–10% of the population, the risk of stone formation and compositional characteristics may exhibit specific alterations; however, the mechanisms by which different thyroid functional states influence stone composition remain unclear. Methods A retrospective analysis was conducted on 33,579 urinary stone composition data collected from 2014 to 2024 in South China. Propensity score matching (PSM) was employed to evaluate the distribution characteristics of stone composition across different thyroid functional states, establishing three 1:1 matched cohorts: hyperthyroidism group (n = 298), hypothyroidism group (n = 140), and hyperparathyroidism group (n = 82). Multivariable logistic regression, generalized linear models, and interaction analyses were performed to assess the associations between stone composition and thyroid disorders, controlling for confounding factors including age, sex, season, and stone location. Results The urinary stone composition analysis in this study revealed specific effects of different thyroid disorders. Patients with hyperthyroidism showed significantly higher proportions of calcium oxalate dihydrate (COD) stones compared to controls (15.1% vs 7.5%, p = 0.016); patients with hypothyroidism exhibited increased proportions of carbonate apatite (CA) stones (85.2% vs 64.3%, p = 0.043). Multivariable regression confirmed hypothyroidism as an independent risk factor for CA stones (OR > 1.0), while demonstrating a protective effect against calcium oxalate monohydrate (COM) stones (OR < 1.0). Interaction analyses revealed sex-based differences in COM stones among hyperthyroid patients (higher predicted probability in males), and seasonal variations in stone composition among hypothyroid patients. Age-stratified analysis identified increasing magnesium ammonium phosphate stones with age in hyperthyroid patients, with CA stones exhibiting the strongest age dependency. Conclusion Urinary stone composition is specifically regulated by thyroid functional states. Hyperthyroidism is associated with increased COD stones, while hypothyroidism independently promotes CA stone formation but inhibits COM stones, suggesting that endocrine factors participate in the formation of different stone types through regulation of calcium-phosphate metabolism, providing important evidence for individualized prevention strategies based on stone composition.