Fluctuations in anti-Mullerian hormone levels throughout the menstrual cycle parallel fluctuations in the antral follicle count: a cohort study

Introduction. In this prospective cohort study we aimed to investigate the hypothesis that fluctuations in anti-Mullerian hormone levels stem from fluctuations in the number of antral follicles. Material and methods. Repeated measurements of anti-Mullerian hormone and antral follicles (follicles 2-8 mm) were performed in 44 women with a regular cycle, during one menstrual cycle. If our hypothesis that anti-Mullerian hormone fluctuations stem from fluctuations in the antral follicles is correct, a fluctuation in the antral follicles would result in an equal and parallel shift in anti-Mullerian hormone. Hence, the difference between antral follicles and anti-Mullerian hormone would remain constant over time. A mixed model analysis, assessing the stability between anti-Mullerian hormone and antral follicles, was performed using the difference between (log)antral follicles and (log)anti-Mullerian hormone. Cohen's D was calculated for the largest of fixed effects in order to assess stability in relative distance between antral follicles and anti-Mullerian hormone. To assess if fluctuation in anti-Mullerian hormone or antral follicles originated from between-subject fluctuation, or from within subject fluctuation, the intra-class correlation coefficient was calculated. Results. Mixed model analysis and Cohen's D (0.12) confirmed the stability of the difference between (log)antral follicles and (log)anti-Mullerian hormone and so confirmed our hypothesis. The good intra-class correlation coefficient (0.73) indicated a small contribution of within-subject variation to anti-Mullerian hormone fluctuations. Conclusions. Fluctuations in anti-Mullerian hormone levels parallel fluctuations in antral follicles, suggesting that anti-Mullerian hormone levels are closely linked to variation in the antral follicles. This knowledge adds to the basic understanding of the origin of anti-Mullerian hormone and could aid in interpretation of individual anti-Mullerian hormone levels.