TPO and autoimmune disease: Endometriosis shares many characteristics with autoimmune diseases, including polyclonal B cell activation, abnormal functions of T and B cells, and inflammatory tissue damage.15 Regarding humoral immunity, the incidence of positive antinuclear antibodies (ANAs) is higher among patients with endometriosis than among control patients; this is also the case in Graves disease.15 In addition to ANAs, the reactivity of some autoantibodies (particularly thyroid peroxidase antibody) is higher in both Graves disease and endometriosis patients.7,16