Evidence suggests that increased gut permeability may be associated with polycystic ovary syndrome (PCOS). Human zonulin is currently the only physiological mediator known to reversibly regulate gut permeability by disassembling intestinal tight junctions. So far, no data on serum zonulin levels in patients with PCOS are available. This study aimed to determine circulating serum zonulin levels in women with PCOS and discuss the relationship between zonulin, insulin resistance, and menstrual disorders in this group.