NORMAL HUMAN FOLLICLE DEVELOPMENT - AN EVALUATION OF CORRELATIONS WITH ESTRADIOL, ANDROSTENEDIONE AND PROGESTERONE LEVELS IN INDIVIDUAL FOLLICLES

OBJECTIVE The mechanism of dominant follicle selection remains obscure . We have investigated the association between follicle diameter and f ollicular steroid levels in individual human ovarian follicles through out the menstrual cycle.DESIGN Fluid from ovarian follicles (n=326) wa s obtained in vivo during surgery from 55 regularly cycling women with proven fertility, Follicles were divided into dominant (diameter >9mm , n=45) and non-dominant (diameter less than or equal to 9mm, n=281) b ased on ultrasound measurements. MEASUREMENTS Fluid was assayed for oe stradiol (EP), androstenedione (AD), and progesterone (P). RESULTS Med ian P and E(2) levels were significantly lower (P<0.0001) and AD level s significantly higher (P=0.03) in non-dominant as compared to dominan t follicles, In non-dominant follicles AD (r=0.14, P=0.02), but not P and E(2), levels were correlated to follicular diameter, and significa nt changes in steroid concentrations across the menstrual cycle were a bsent, In dominant follicles, diameter was positively correlated with P and E(2) (P < 0.001) levels, and inversely correlated with AD concen trations (P=0.01). CONCLUSIONS Results indicate that (1) intrafollicul ar oestradiol concentrations rise only in follicles exceeding 9 mm in diameter and correlate with the diameter of these dominant follicles, suggesting that significant increase in aromatase enzyme activity occu rs only in the dominant follicle (2) a cycle-independent accumulation of androstenedione with size occurs in non-dominant follicles, and (3) progesterone production occurs in the largest dominant follicles only , suggesting a limited, if any, role for progesterone during follicle development.