IL6 and inflammatory bowel disease: However, there is substantial evidence in the medical literature that osteoprotegerin (OPG) levels are associated with inflammatory states and correlate with established inflammatory markers such as C-reactive protein (CRP), interleukin-6 (IL-6), and erythrocyte sedimentation rate (ESR) in various conditions, including chronic kidney disease, infection-induced inflammation, and inflammatory bowel disease [31,32,33,34].