*Inflammatory Pathways Linking Synovial and Thyroid Tissue Damage*

Inflammatory pathways linking synovial and thyroid tissue damage highlight the shared immunopathological mechanisms underlying rheumatoid arthritis and autoimmune thyroid diseases. Both tissues are affected by loss of immune tolerance, leading to chronic infiltration of immune cells such as T lymphocytes, B lymphocytes, macrophages, and dendritic cells. These immune cells release pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β), and interleukin-17 (IL-17), which perpetuate local inflammation and promote tissue destruction. A central feature of this inflammatory link is the imbalance between T helper 17 (Th17) cells and regulatory T cells (Tregs). Excessive Th17 activity enhances inflammatory signaling, while impaired Treg function fails to suppress autoreactive immune responses. This imbalance contributes to synovial hyperplasia, cartilage erosion, and bone damage in rheumatoid arthritis, as well as follicular cell apoptosis, fibrosis, and hormonal dysfunction in autoimmune thyroid diseases.