We are pleased to share our new publication, titled “IL-34 as a Novel Mediator Linking Vitamin D Deficiency with Osteoporosis and Knee Osteoarthritis”, published in the International Journal of Molecular Sciences. Our study reveals that vitamin D deficiency is strongly associated with elevated IL-34 levels, intensified inflammatory activity, and a higher risk of osteoporosis and knee osteoarthritis. We demonstrate that IL-34 plays a central mechanistic role linking low vitamin D status with bone loss and joint degeneration. These findings highlight IL-34 as a promising biomarker and a potential therapeutic target. https://doi.org/10.3390/ijms262211090 Figure legend. Illustrative clinical cases with biomarker profiles and knee radiographs. The side of each knee right (R) or left (L) is clearly labeled, and arrows indicate the side or area of special clinical relevance (such as severe deformity). Case A (Healthy control): 55-year-old woman with FM/WT (0.31), VDD (25(OH)D = 37 nmol/L),...