IntroductionPrevious　research　has　demonstrated　that　even　minor　changes　in　thyroid　function　are　associated　with　an　increased　risk　of　osteoporosis　(OP).　However,　the　causal　relationship　between　thyroid　disorders　and　the　development　of　OP　remains　unclear.　To　address　this,　we　aim　to　investigate　the　connection　between　genetic　predispositions　to　various　thyroid　disorders　and　OP　using　a　two-sample　Mendelian　randomization　(MR)　approach.Materials　and　methodsInstrumental　variables　(IVs)　for　multiple　thyroid　disorders　were　sourced　from　a　large　genome-wide　association　study　(GWAS)　meta-analysis　dataset.　Summary-level　data　for　OP　were　obtained　from　the　FinnGen　consortium.　Inverse　variance　weighting　(IVW)　methods　served　as　the　primary　approach　for　MR　analysis.　Sensitivity　analyses　included　MR-Egger　regression,　heterogeneity　testing,　multiple　validity　tests,　and　leaFve-one-out　sensitivity　tests.ResultsIVW　analysis　revealed　a　direct　causal　effect　of　hypothyroidism　(OR　=　1.105,　95%　CI　1.023-1.194,　P　0.011)　and　Hashimoto＇s　thyroiditis　(OR　=　1.142,　95%　CI　1.026-1.271,　P　0.015)　on　OP.　However,　no　direct　causal　association　was　found　between　hyperthyroidism　(OR　=　1.030,　95%　CI　0.944-1.123,　P　0.508)　or　thyroid　cancer　(OR　=　0.971,　95%　CI　0.898-1.051,　P　0.469)　and　OP.ConclusionOur　MR　analysis　revealed　a　causal　association　between　hypothyroidism,　Hashimoto＇s　thyroiditis,　and　OP.　This　highlights　the　significant　impact　of　thyroid　function　on　bone　health.　However,　further　longitudinal　studies　are　needed　to　confirm　these　findings　conclusively.