Biochemical Assessment The participants will be instructed to fast 12 hours prior to the blood sampling for analysis. A stool sample as well as a 5 ml venous blood sample will be collected from the patients in order to determine biochemical parameters. The University Hospital routine laboratory will analyze the venous blood, the levels of C-reactive protein (CRP), calcium, 25-hydroxyvitamin D, parathyroid hormone (PTH) and inflammatory cytokines such as Interleukins (IL) 17, IL 6 and Tumor necrosis factor alfa (TNF-α) . Fecal calprotectin dosage will be performed in the stool samples. CRP and serum calcium are routinely evaluated in all CD patients under follow-up in the inflammatory bowel disease clinic at HU/CAS.