“…Follicular steroids are secreted by granulosa and theca cells under the control of gonadotropins, and the hormonal microenvironment affects the development of the follicles and viability of the oocytes (Speroff, Glass, & Kase, 1999). In normal ovulatory cycles, a higher concentration of E2 in follicular fluid (FF) is associated with healthy follicles that contain oocytes capable of meiosis, and higher concentrations of androgens indicative of atretic changes (degeneration and subsequent resorption of the follicles) (Greenwald & Roy, 1994;Speroff, Glass, & Kase, 1999). The majority of earlier studies of steroids in ovarian follicles (McNatty et al, 1979;Dehennin, Jondet, & Scholler, 1987a,b;Itskovitz et al, 1991) were undertaken to obtain prognostic parameters for the likelihood of a successful implantation during in vitro fertilization (IVF); however, the relationship between steroid hormones and follicular development in regularly menstruating (RM) healthy women was not well studied.…”