In order to investigate whether high serum INS levels in endometriosis patients were related to insulin resistance, we further calculated the HOMA index (Glu × INS/22.5) and found no significant difference between the two groups [2.50 (1.07–2.09) vs 1.53 (1.10–2.09), P = 0.193], indicating that the increase of insulin levels in endometriosis patients was not caused by insulin resistance. This evidence concerns the gene INS and endometriosis.