also become widely used in the evaluation of testicular presence and function in infants with intersex conditions, ambiguous genitalia, and cryptorchidism. A study published in Nature Medicine found a link between hormonal imbalance in the womb and polycystic ovary syndrome (PCOS), specifically prenatal exposure to anti-Müllerian hormone. For the study, the researchers injected pregnant mice with AMH so that they had a higher than normal concentration of the hormone. Indeed, they gave birth to daughters who later developed PCOS-like tendencies. These included problems with fertility, delayed puberty, and erratic ovulation. To reverse it, the researchers dosed the polycystic mice with an IVF drug called cetrorelix, which made the symptoms to go away. These experiments should be confirmed in humans, but it could be the first step in understanding the relationship between the polycystic ovary and the anti-Müllerian hormone. Blood levels In healthy females AMH is either just detectable or undetectable in cord blood at birth and demonstrates a marked rise by three months of age; while still detectable it falls until four years of age before rising linearly until eight years of age remaining fairly constant from mid-childhood to early adulthood – it does not change significantly during puberty. The rise during childhood and adolescence is likely reflective of different stages of follicle development. From 25 years of age AMH declines to undetectable levels at menopause. The standard measurement of AMH follows the Generation II assay. This should give the same values as the previously used IBC assay, but AMH values from the previously used DSL assay should be multiplied with 1.39 to conform to current standards because it used different antibodies. Weak evidence suggests that AMH should be measured only in the early follicular phase because of variation over the menstrual cycle. Also, AMH levels decrease under current use of oral contraceptives and current tobacco smoking. Reference ranges Reference ranges for anti-Müllerian hormone, as estimated from reference groups in the United States, are as follows: Females: Males: AMH measurements may be less accurate if the person being measured is vitamin D deficient. Note that males are born with higher AMH levels than females in order to initiate sexual differentiation, and in women, AMH levels decrease over time as fertility decreases as well. Clinical usage General fertility assessment Comparison of an individual's AMH level with respect to average levels is useful in fertility assessment, as it provides a guide to