Antimüllerian hormone levels and numbers and sizes of antral follicles in regularly menstruating women of reproductive age referenced to true ovulation day.

Objective: To assess menstrual cycle antimüllerian hormone (AMH) levels in reproductive age women and which/how many follicles substantially produce AMH.

Design: Prospective study of menstruating women using mixed-effects models to analyze AMH variability and correlation of follicle counts/size classes to AMH levels.

Setting: Clinic.

Patient(s): Regular menstruating women with ovulatory cycles (n = 40, aged 18-37 years) and no known subfertility.

Intervention(s): Women collected daily urine samples and visited the study center for blood samples/transvaginal ultrasound during one complete menstrual cycle (visits were every 2 days; daily from follicle size >16 mm until postovulation).

Main Outcome Measure(s): AMH levels throughout the menstrual cycle, correlated with antral follicles as observed by ultrasound and identification of follicles producing AMH.

Results: Of all antral follicles visible by high-resolution ultrasound, AMH is produced substantially only by follicles up to 7 mm in diameter. For women with basal AMH >1 ng/mL, mean AMH concentrations vary across ovulatory menstrual cycles, showing a statistically significant decrease from -5 to 2 days after objective ovulation; significantly lower mean luteal AMH levels (-7.59% to mean follicular AMH) are detected. The number of antral follicles can be estimated from AMH (ng/mL) levels using the modified Beckman Coulter Generation II AMH assay for any day of the follicular phase.

Conclusion(s): AMH concentrations vary across ovulatory menstrual cycles, showing a significant periovulatory decrease. The number of small antral follicles can be estimated from preovulatory AMH levels with relevance for patient management.

Clinical Trial Registration Number: NCT01802060.