While previous studies have shown an association between anti-Mullerian hormone (AMH) levels and endometriosis, there are limited data on the relationship between AMH levels and age among women with endometriosis.

The present study aimed to investigate the associations between age and AMH levels in women with and without endometriosis.

A cross-sectional, population-based study using data from the ongoing Tehran Lipid and Glucose Study.

A total of 1005 eligible reproductive-age women were selected. These participants were categorised into two groups: women with confirmed endometriosis (n=305) and controls (n=700).

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Association between AMH levels and age among women with endometriosis and healthy controls, using linear, quadratic and segmented regression analyses.

A total of 1005 women aged 18–48 years participated in the study, including 305 (30.3%) with endometriosis and 700 (69.7%) healthy controls. Women with endometriosis had significantly lower AMH levels compared with healthy controls (1.99±1.42 vs 2.30±1.61 ng/mL; p=0.029). In healthy controls, an increase of 1 year was associated with –0.15 ng/mL of AMH (95% CI: –0.17 to –0.14). Segmented regression identified a threshold at 27 years (1.92), with a sharper decline below this age (slope: –0.35, 95% CI: –0.47 to –0.23; p

Our study showed that women with endometriosis had significantly lower AMH levels compared with healthy controls and did not demonstrate the age-related threshold observed in the control group, where AMH levels declined more sharply before 27 years of age. These findings suggest that endometriosis may alter the typical pattern of AMH, indicating that clinicians should interpret AMH levels with caution in this population. Further research is needed to validate these results in other populations and explore alternative biomarkers or strategies for more accurately assessing ovarian reserve in women with endometriosis.