Abstract: The insulin-like factor 3 （INSL3），previously known as the relaxin-like factor，is encoded by the INSL3 gene in human. It is secreted from the testicular leydig cells of adult men as well as the theca interna cells of ovarian follicles in adult female. Recent studies have found that INSL3 circulating levels in patients with polycystic ovary syndrome are significantly higher than that in normal people，especially in those patients who are not overweight，which possibly due to the reason of luteinizing hormone dependent hyperandrogenism. This paper describes the INSL3 gene and its molecular structure，its receptor （a novel G-protein-coupled receptors LGR8/GREAT），the physiological function in female，with particular emphasis on the vital influence of pathogenesis and pathophysiology of polycystic ovary syndrome caused by INSL3.

Key words: Polycystic ovary syndrome, Hyperandrogenism, Luteinizing hormone, Insulin resistance, Receptors, G-protein-coupled