Polycystic ovary syndrome was defined as the combination of anovulation and hyperandrogenaemia (NIH 1990). Another definition used the combination of ultrasonographic appearance of polycystic ovaries and/or anovulation and/or hyperandrogenaemia or cutaneous manifestations of hyperandrogenism (Rotterdam). The population defined according to NIH is probably in greater risk of insulin resistance and obesity. Pathogenesis of PCOS is not clear till now. Dysregulation of ovarian steroidogenesis could be one of the causes of the full-blown syndrome. Up-regulation of steroidogenic enzymes, probably due to the exaggerated expression of transcription factors such as GATA-6 or retinoids could be involved. Insulin sensitisators are now widely used in the therapy. They could beneficially modify not only insulin resistance and dyslipidaemia, but also ovarian and adrenal steroidogenesis. Metformin and glitazones improve anovulation however the studies conducted till now were not representative concerning the point of successful pregnancy.

        Key words: polycystic ovary syndrome, steroid hormone, insulin resistance, metformin.