Hyperthyroidism increases the risk of osteoarthritis in individuals aged 60-80 years

To elucidate the currently unknown relationship between hyperthyroidism and osteoarthritis (OA). During 2007-2012, 7,433 participants (hyperthyroidism patients = 125; OA patients = 675) were included in the National Health and Nutrition Examination Survey database. We used a weighted multivariable-adjusted logistic regression analysis to assess the association between hyperthyroidism and OA. We also assessed the causality of that relationship using publicly available genome-wide association study data and three Mendelian randomization (MR) analysis methods. The heterogeneity test, pleiotropy test, and leave-one-out tests were used for sensitivity analysis. In this cross-sectional study, after adjusting for potential confounding factors, we found that hyperthyroidism significantly (P = 0.018) increased the risk of OA (odds ratio [OR] = 2.23, 95% confidence interval [CI] = 1.2-4.17). Age-stratified analysis revealed that hyperthyroidism was associated with a greater risk of OA in the 60-80-year-old age group (OR = 2.86, 95% CI = 1.46-5.59, P = 0.002), with no significant association in the 18-59-year-old age group (all P > 0.05). The results of the inverse-variance weighting (IVW) analysis showed that hyperthyroidism increased the risk of OA (OR = 1.23, 95% CI = 1.04-1.46; P = 0.017). The weighted median estimator (WME) and MR-Egger method also confirmed this causal association (OR = 1.27 and OR = 1.32, respectively). The sensitivity analysis results confirmed the reliability of this conclusion. In addition, IVW-based reverse-MR analysis revealed that OA did not increase the risk of hyperthyroidism (OR = 1.02, 95% CI = 0.97-1.08; P = 0.449). Hyperthyroidism is associated with an increased risk of OA, but the underlying pathological mechanism still needs to be clarified in future research.