Correlation of serum estradiol levels and ultrasound monitoring to assess follicular maturation.

Thirty-eight patients underwent 38 cycles of induction of ovulation using stepwise human menopausal gonadotropin and human chorionic gonadotropin (hCG) administration. Ultrasonography was performed on the day of hCG injection. The mean age +/- standard error of the mean (SEM) of the patients was 32.9 +/- 0.8 years, and the duration of infertility ranged from 1 to 14 years (median, 2.8). Ultrasonographic measurements were obtained of the largest diameter and the volume of the dominant follicles as well as all other follicles in both ovaries. Data were analyzed by Student's t-test, regression analysis, and analysis of variance. The mean +/- SEM diameter of dominant follicles was 1.8 +/- 0.1 cm, and the volume of dominant follicles was 3.5 +/- 0.8 cm. The mean +/- SEM serum estradiol (E2) level before hCG administration was 659 +/- 62 pg/ml. Significant correlations were found between preovulatory serum E2 levels and the total follicular volume of both ovaries (r = 0.41, P less than 0.05) and follicular volume of the ovary containing the dominant follicle (r = 0.42, P less than 0.01). No significant correlation was observed between the diameter of the dominant follicle and serum E2 levels. These results suggest that ultrasound findings reflect growth, whereas serum E2 levels primarily detect functional activity of follicles.