IgG: Immunoglobulin G, RU: relative units, IBS: Irritable bowel syndrome, IBD: Inflammatory bowel disease, GI: gastrointestinal, GnRH: gonadotropin-releasing hormone, OR: odds ratio, CI: confidence interval, P: p-value, LH: luteinizing hormone, ELISA: enzyme-linked immunosorbent assay. Here, PLOD1 is linked to inflammatory bowel disease.