The present invention related to a pharamaceutical composition for preventing rheumatoid arthritis and osteoporosis, comprising an effective amount of IL-20 antagonist, wherein the first antibody is an anti-IL20 antibody or anti-IL20 antigen binding fragments and a pharamaceutically accectable carrier, expcipient or stabilizing agent.本發明係關於一種預防類風濕性關節炎或骨質疏鬆症之醫藥組成物,該醫藥組成物包含一有效劑量之介白素-20拮抗劑,其中該介白素-20拮抗劑為抗介白素-20抗體或抗介白素-20抗原結合片段;以及一醫藥上可接受之載體、賦形劑或安定劑。