How long does combined hormonal therapy suppress AMH levels in women with endometriomas? Results from an exploratory analysis of a clinical trial

Background: Lower Anti-Müllerian hormone (AMH) levels have been observed in women with ovarian endometriomas (OMA) undergoing combined hormonal contraceptive (CHC) therapy. However, the extent and timing of AMH recovery after CHC discontinuation remains unclear in this population. The objective of our study was to prospectively evaluate changes in serum AMH levels at hormonal therapy beginning, throughout treatment, and up to three months following CHCs discontinuation in women with OMAs. Methods: This prospective, observational cohort study was conducted at a tertiary endometriosis center between March 2020 and December 2022. Consecutive patients with OMA were enrolled. Exclusion criteria included prior ovarian surgery, ongoing hormonal therapy, and contraindications to CHC. Serum AMH was measured at baseline (T0), after six months of CHC treatment (T1), and three months post-discontinuation (T2). Secondary outcomes included evaluating AMH changes based on presence of deep infiltrating endometriosis (DIE), OMA laterality, number, age. Results: AMH levels declined significantly by 0.21 ng/mL from T0 to T2 (p = 0.027). No significant influence was observed from deep infiltrating endometriosis (DIE), OMA laterality, number, nor age. AMH decreased more from T0 to T1 in women with OMAs <30 mm versus >30 mm (p = 0.005) and significantly increased from T1 to T2 in the <30 mm group (p = 0.018). However, overall AMH variation from T0 to T2 did not differ between size groups. Conclusions: In our study, AMH levels significantly decreased after six months of CHC therapy and remained reduced three months after discontinuation, compared to pretreatment values, in women with OMAs, regardless of clinical or ultrasound characteristics. These findings suggest that a three-month washout period may be insufficient to distinguish the transient effects of CHC use from underlying ovarian impairment, and thus inadequate for accurately assessing ovarian reserve in this population. Larger prospective studies are needed to validate these results and to determine the optimal timing for AMH testing following CHC discontinuation.