Anti-Müllerian Hormone (AMH) is a protein hormone produced by the small, developing follicles within the ovaries. This hormone serves as a measurable marker that reflects a woman’s remaining supply of eggs, often referred to as her ovarian reserve. An AMH blood test provides an estimate of the number of eggs currently resting in the ovaries, giving clinicians valuable insight into reproductive potential. While it does not offer a complete picture of fertility, understanding AMH levels is a routine step in assessing the reproductive timeline.
The Role of AMH in Fertility
AMH is primarily secreted by the granulosa cells surrounding the eggs in the preantral and small antral follicles. These are the microscopic follicles that are continuously recruited from the large, dormant pool of primordial follicles present in the ovaries. Measuring the concentration of AMH in the bloodstream offers a reliable, indirect assessment of the size of this resting egg pool.
A higher AMH level generally correlates with a greater quantity of remaining follicles, indicating a larger ovarian reserve. Conversely, a lower AMH level suggests a smaller pool of eggs is available for future recruitment. Because AMH is produced by follicles that are not dependent on the monthly cycle, its level remains relatively stable throughout the menstrual cycle, making it a convenient and consistent measure of ovarian quantity. The overall trend of AMH levels declining with advancing age reflects the natural, continuous depletion of the ovarian follicle reserve over a woman’s reproductive lifespan.
Interpreting AMH Levels: What the Numbers Mean
The concept of a “good” AMH level is entirely contextual, depending on a woman’s age and whether she is attempting natural conception or assisted reproduction. AMH results are commonly reported in two different units: nanograms per milliliter (ng/mL) or picomoles per liter (pmol/L). For practical interpretation, a general range of 1.0 to 3.0 ng/mL is often considered average or satisfactory for women of reproductive age.
Levels in the satisfactory range, typically above 1.0 ng/mL (or approximately 7.14 pmol/L), suggest a robust ovarian reserve that will likely respond well to fertility treatments like In Vitro Fertilization (IVF). Women with levels in the optimal range, potentially 1.5 ng/mL and above, generally have the best prognosis for retrieving a sufficient number of eggs during a stimulation cycle.
A level below 1.0 ng/mL indicates a diminished ovarian reserve, which may suggest that fewer eggs will be retrieved during an IVF cycle. Readings below 0.5 ng/mL (around 3.5 pmol/L) are generally considered very low and suggest a severely reduced response to fertility medication. However, women with very low AMH levels can still conceive both naturally and with assistance, although the likelihood of a successful egg retrieval is reduced.
The specific numerical ranges for AMH should always be interpreted against age-specific norms, as a level considered low for a woman in her early 30s may be entirely expected for a woman in her early 40s. Furthermore, very high AMH levels, often exceeding 3.5 ng/mL or more, can signal a different reproductive profile. These elevated levels are frequently associated with Polycystic Ovary Syndrome (PCOS), where a large number of small follicles produce excess AMH.
Factors That Influence AMH Levels
Age is the strongest determinant of AMH levels, with a predictable and gradual decline occurring over time as the pool of eggs is naturally depleted. This decline accelerates significantly after the mid-thirties, reflecting the biological timeline of ovarian aging. Genetics also play a role, as a family history of early menopause can suggest a naturally lower starting reserve or a faster rate of decline.
Conditions affecting the ovaries directly can cause AMH levels to be lower than expected for a woman’s age. For instance, prior ovarian surgery, such as procedures to remove endometriomas (endometriosis cysts), can inadvertently damage the surrounding ovarian tissue containing the follicles. Certain medical treatments, including chemotherapy and radiation, are known to be toxic to follicles and can lead to a sharp, irreversible drop in AMH.
Conversely, conditions like Polycystic Ovary Syndrome (PCOS) can lead to artificially elevated AMH levels. Women with PCOS have an accumulation of numerous small follicles that fail to develop properly, and the high number of these follicles producing AMH results in a high blood concentration. Certain lifestyle factors, such as smoking, are also consistently linked to lower AMH levels and a faster rate of ovarian reserve depletion.
Hormonal contraception can temporarily suppress AMH readings by up to 30%. This suppression occurs because the hormones in the birth control pill inhibit the growth of the small follicles that produce AMH. If a woman is tested while using hormonal contraception, her AMH result may not accurately reflect her true underlying ovarian reserve.
AMH Limitations and Next Steps
AMH is an excellent measure of egg quantity, but it does not provide any information about the quality of the remaining eggs. Egg quality, which refers to the genetic health of the egg, is the single most important factor for achieving a healthy pregnancy and is primarily determined by age. A woman can have a low AMH level, indicating a small number of eggs, but if she is young, the quality of those few eggs is likely to be high, leading to good pregnancy potential.
For this reason, AMH should never be used as a standalone test for predicting the likelihood of natural conception or live birth. Clinicians typically combine the AMH result with other fertility markers to create a more complete profile of ovarian function. These complementary tests include a transvaginal ultrasound to measure the Antral Follicle Count (AFC) and a blood test for Follicle-Stimulating Hormone (FSH). The AFC involves counting the number of small, visible follicles on the ovaries, providing a direct snapshot of the available eggs, while FSH levels indicate how hard the brain is working to stimulate the ovaries.
For individuals undergoing assisted reproduction, the AMH result is directly incorporated into treatment planning. For example, a low AMH may prompt a doctor to use a higher dose of stimulating medications during IVF. Conversely, a very high AMH requires a lower, more cautious approach to prevent Ovarian Hyperstimulation Syndrome.