These complications arise because of the genetically determined cause of the PCOS i.e. hyper- secretion of androgens from the ovary which favours excess luteinizing hormone (LH) secretion and insulin resistance. However, insulin resistance with or without a genetic mutation may be the initiator, followed by hyper-androgenism. Thus, insulin resistance is an important contributing factor to abnormal steroidogenesis in PCOS because hyper-insulinemia stimulates the pathway of insulin like growth factor-I (IGF-I) in theca cells of the ovary by cross-reacting with the receptors of IGF. Stimulation of the ovarian theca cells increases the production of androgens (eg, testosterone, androstenedione) which in turn, blocks the down-regulation of androgens by LH surge and leads to the hyper-androgenic environment in the ovary. Because of a decreased level of FSH relative to LH, the ovarian granulosa cells cannot aromatize the androgens to estrogens, which lead to decreased estrogen levels and results in anovulation.