Epidermal growth factor in small antral ovarian follicles of pregnant women

Levels of epidermal growth factor (EGF) and steroids were measured by radioimmunoassay in follicular fluid (FF) aspirated from 114 small antral follicles with diameters from 1 to 6 mm and in serum from 19 women undergoing Caesarean section at term. Concentrations of EGF in FF were inversely and significantly correlated to follicular size, being 4.7 +/- 0.4 (mean +/- S.E.M.) nmol/l in follicles of 1-2 mm in diameter and declining to 2.2 +/- 0.2 and 1.4 +/- 0.2 nmol/l in follicles of 3-4 mm and 5-6 mm in diameter respectively. The mean +/- S.E.M. concentration of EGF in serum (0.7 +/- 0.03 nmol/l) was significantly lower than that in FF. Levels of EGF, progesterone and oestradiol in FF were not significantly correlated to one another. In contrast to EGF, levels of progesterone and oestradiol in FF did not vary significantly with follicular diameter in these small follicles. On the basis of these results we suggest that EGF is synthesized in small human antral follicles, and that EGF stimulates granulosa cell proliferation and follicle growth up to 6 mm in diameter. Furthermore, the high intrafollicular levels of EGF may protect the small follicles against untimely effects of high levels of FSH, for instance during the mid-cycle surge of gonadotrophins. It is concluded that EGF plays an important role as an autocrine and/or paracrine regulator of development of small antral follicles in women.