Anti-Müllerian Hormone (AMH) is a protein produced by the granulosa cells within the ovarian follicles. Measuring AMH in the blood estimates the remaining supply of eggs, or ovarian reserve. The level of AMH remains relatively stable throughout the menstrual cycle, making it a convenient marker for ovarian function. Women diagnosed with Polycystic Ovary Syndrome (PCOS) consistently show higher AMH levels, and this elevated hormone is considered a strong indicator associated with the presence of PCOS.
The Biological Basis of Elevated AMH
The increased concentration of AMH in women with PCOS reflects a disruption in the normal process of follicle development within the ovaries. Follicles are small, fluid-filled sacs that house immature eggs, and the granulosa cells lining them are the source of AMH. The hormone is primarily secreted by the small, non-dominant antral follicles.
In a normal cycle, a cohort of these small follicles begins to develop, and one typically becomes dominant, leading to ovulation. Polycystic Ovary Syndrome is characterized by a failure of these developing follicles to mature fully and ovulate. This causes them to accumulate beneath the ovarian surface, leading to an excessive number of small, resting antral follicles, a condition known as polycystic ovarian morphology (PCOM).
Since each accumulated small follicle continues to produce AMH, the total amount of the hormone released into the bloodstream becomes significantly higher than in healthy women. Research suggests that the granulosa cells in women with PCOS may also intrinsically produce more AMH per follicle. The elevated serum AMH level is a direct biochemical reflection of the excessive pool of small ovarian follicles characteristic of the syndrome.
Defining the AMH Threshold for PCOS
The specific serum AMH level that indicates PCOS is a subject of ongoing research, and a single, universally accepted cutoff value does not yet exist. Thresholds vary significantly depending on the laboratory assay used, the population studied, and the specific diagnostic criteria applied. Generally, women with PCOS exhibit AMH levels that are two to four times higher than those of healthy women of the same age.
Many studies have proposed cutoff values, which a physician must interpret alongside other clinical findings. For example, some research suggests a threshold greater than 5 nanograms per milliliter (ng/mL) can differentiate women with PCOS. Cutoffs have been proposed ranging from 3.19 ng/mL to 7.51 ng/mL, highlighting the impact of ethnicity and the specific assay used.
When AMH is measured in picomoles per liter (pmol/L), the proposed diagnostic thresholds show similar variability. Values greater than 35 pmol/L have been found to offer high sensitivity for identifying polycystic ovarian morphology. Reported cutoffs have ranged from 10 pmol/L up to 57 pmol/L in different international guidelines, underscoring the lack of standardized testing. A physician will always use the reported level as a piece of evidence rather than a definitive diagnosis on its own.
Integrating AMH into the Diagnostic Criteria
While elevated AMH is strongly associated with PCOS, it is not currently a standalone diagnostic tool, but rather a promising biomarker integrated into the broader diagnostic framework. Polycystic Ovary Syndrome is most commonly diagnosed using the Rotterdam criteria, which require a patient to exhibit at least two out of three specific features: oligo- or anovulation (irregular or absent periods), clinical or biochemical hyperandrogenism (signs of elevated male hormones), and polycystic ovarian morphology (PCOM) seen on ultrasound.
AMH has emerged as a potential non-invasive alternative to the transvaginal ultrasound required to confirm PCOM. The hormone level correlates closely with the Antral Follicle Count (AFC) on ultrasound, which counts the number of small follicles. Replacing the subjective and equipment-dependent ultrasound finding with a standardized blood test offers a more objective and convenient method to meet the PCOM criterion.
Studies have shown that replacing PCOM with an AMH threshold, when combined with the other two Rotterdam criteria—oligo/anovulation and hyperandrogenism—can maintain or even increase the diagnostic accuracy. Combining a specific AMH cutoff with the presence of irregular periods and/or signs of androgen excess has shown high sensitivity and specificity in various study populations.
Factors That Influence AMH Levels
The measurement of AMH is subject to several physiological and technical factors that can temporarily alter the result, necessitating careful interpretation. Age is the most well-known variable, as AMH levels naturally decline over time, reflecting the normal decrease in ovarian reserve. This means that a specific AMH number must always be considered relative to a woman’s reproductive age.
The use of hormonal contraceptives is another significant factor that can artificially suppress AMH levels. Women actively using hormonal birth control, such as combined oral contraceptive pills, may have AMH levels that are lower than those not using them. This suppressive effect is temporary and reversible, but an AMH test taken while on contraception may underestimate the true ovarian reserve.
Additionally, laboratory variations, including the type of assay used and the specific reagents, contribute to the lack of a single international standard for AMH measurement. Other factors, such as Vitamin D deficiency, have been linked to lower AMH levels, suggesting that nutritional status may also play a role in the hormone’s signaling and production. These variables highlight why clinical judgment remains paramount when using AMH to support a PCOS diagnosis.