Healthy controls expressed low levels of GnRH IgM antibodies with a prevalence of 23%. The prevalence of GnRH IgM antibodies in IBS and dysmotility patients was 42% (P = 0.008), and the levels were higher (P = 0.000). Patients with diabetes mellitus expressed GnRH IgM antibodies in the same prevalence as controls (25%), but at higher levels (P = 0.02). Patients with celiac disease or IBD had the same or lower levels of antibodies. There were no associations between antibodies, other co-existing diseases, or laboratory analyses. This evidence concerns the gene CD40LG and irritable bowel syndrome.