Polycystic ovary syndrome (PCOS) is perhaps the most prevalent endocrine disorder in women of reproductive age, characterized by elevated levels of circulating androgens or clinical manifestations of androgen excess. The specific cytokine profile of PCOS patients is probably related to the lower implantation rate, since follicular fluid appears to function as an embryotrophic agent. For a better understanding of the local regulation of human follicles, the present study investigated the protein expression levels and cellular localization of HOXA 10 in granulosa cells (GCs) from women with normal ovarian function undergoing IV F due to their husbands suffering from azoospermia. We demonstrated by immunohistochemical studies that the expression of HOXA 10 was mainly localized in the cytoplasm of GCs. Our data indicate that these alterations were associated with changes in the expression of ovarian transcription factors of HOXA 10. GC dose-responsive decreases in HOXA 10 protein were observed in response to physiological or supraphysiological concentrations (10(-4) to 10(-7) M) of testosterone. These data reveal that testosterone may be involved in HOXA 10 gene regulation in GCs. Decreased HOXA 10 expression in GCs treated with testosterone suggest that this androgen is responsible for the decreased expression of HOXA 10 in PCOS patients.