Many studies have used dorsal root ganglion (DRG) cells to study the effect of nerve growth factor, thromboxane A2 derived from peritoneal fluid of patients with endometriosis, and insulin-like growth factor 1 derived from macrophages on nerve growth, thus proving its involvement in the generation of pain symptoms in endometriosis (12, 44, 45). The gene discussed is NGF; the disease is endometriosis.