Background
To determine normal ranges for serum anti‐Mullerian hormone (AMH) using the new automated Elecsys® AMH assay platform, with a view to establishing values that signify premature loss of ovarian reserve, increased risk for an excessive response during IVF stimulation and a likely diagnosis of polycystic ovary syndrome (PCOS).

Materials and Methods
Serum AMH was measured by the Elecsys® automated electrochemiluminescence assay in 654 women undergoing gynaecological assessment.

Results
Serum AMH levels peaked before 25 years of age, with mean AMH levels halving by 36 and falling to a quarter of their peak by 40 years of age. Overall, AMH results of 95% of patients with PCOS exceeded the 50th percentile for their age, with 72.1% having an AMH result in the top quartile for age. ROC analysis suggested that a serum AMH ≥36 pmol L−1 is the best determinant of PCOS status (sensitivity 83.7% and specificity 82.3%). Serum AMH exhibited an excellent correlation with ultrasound‐assessed antral follicle count (AFC) (r = 0.836, P < 0.0001), with a result of 20 pmol L−1 corresponding to an AFC of 16 and, therefore, increased risk of ovarian hyperstimulation syndrome (OHSS) during IVF treatment. Conclusion Serum AMH is a sensitive marker of age‐related decline in ovarian reserve status. A serum AMH result >36 pmol L−1, or above the 75th percentile for age, is highly suggestive of a diagnosis of PCOS. A serum AMH result below the 10th percentile for age suggests accelerated loss of ovarian reserve, while an AMH result exceeding 20 pmol L−1 suggests an increased risk of OHSS during IVF treatment.