Anti-Müllerian Hormone (AMH) is a protein hormone produced by the ovaries used to assess a woman’s remaining egg supply, known as ovarian reserve. It is secreted by the granulosa cells surrounding the immature eggs within the small, developing follicles. Measuring AMH is performed through a simple blood test, providing a numerical estimate of the available egg pool. This measurement, typically expressed in nanograms per milliliter (ng/ml), helps inform discussions about fertility, family planning, and potential responses to assisted reproductive technologies.
The Role of AMH in Ovarian Reserve
AMH production begins in the pre-antral and small antral follicles. The level of AMH detected in the bloodstream is directly correlated with the number of these small, growing follicles present in the ovaries. AMH serves as a proxy for ovarian reserve because the number of these follicles reflects the overall size of the remaining egg pool. Unlike hormones such as Follicle-Stimulating Hormone (FSH) or Estradiol, which fluctuate dramatically throughout the menstrual cycle, AMH levels remain relatively stable, allowing the test to be administered at any point. AMH levels also decline significantly earlier than FSH levels begin to rise, making it a sensitive indicator of declining ovarian reserve.
Standard AMH Levels by Age
AMH levels naturally decrease over time as the fixed pool of eggs is steadily used up throughout a woman’s reproductive years. While individual variation is significant, a general pattern of decline has been established. For women in their early to mid-twenties, median AMH levels are typically highest, often ranging between 3.0 and 4.0 ng/ml. The median level begins a gradual decline in the late twenties; women aged 30 to 34 often see levels between 1.5 and 4.5 ng/ml, with a median around 2.5 ng/ml. The decline becomes more pronounced after the mid-thirties. By age 35 to 39, the median AMH level drops to approximately 1.5 ng/ml, with a typical range of 1.0 to 3.0 ng/ml. For women in their early forties, levels frequently fall below 1.0 ng/ml, often ranging from 0.5 to 2.0 ng/ml. AMH is a measure of egg quantity, not egg quality, which is primarily determined by age.
Interpreting AMH Results
Beyond the standard age-based chart, AMH results are interpreted based on specific numerical cutoffs that indicate the current state of ovarian health. A result that falls within the “Optimal” or “Normal” range (1.0 ng/ml to 4.0 ng/ml) suggests that the ovarian reserve is adequate. Levels within this range generally predict a good response to ovarian stimulation medications used in treatments like In Vitro Fertilization (IVF).
Results falling below the 1.0 ng/ml threshold commonly define Diminished Ovarian Reserve (DOR). Levels between 0.5 ng/ml and 1.0 ng/ml are considered low, while readings below 0.5 ng/ml are deemed severely low. A low AMH result means fewer eggs are available for retrieval during IVF, necessitating adjusted treatment protocols. However, a low AMH level does not automatically predict the inability to conceive naturally, as only one healthy egg is needed per cycle.
Conversely, very high AMH readings, typically above 4.0 ng/ml, often suggest a different clinical picture. The most common cause of an elevated AMH level is Polycystic Ovary Syndrome (PCOS). This condition is characterized by an excessive accumulation of small, AMH-producing follicles that fail to mature and ovulate, leading to an artificially inflated AMH number. High AMH in the context of PCOS can signal potential issues with spontaneous ovulation. For women undergoing IVF, a very high AMH level significantly increases the risk of Ovarian Hyperstimulation Syndrome (OHSS). Fertility specialists use these high readings to modify the dose of stimulation medications, ensuring a safer treatment cycle.
Factors That Influence AMH Levels
AMH levels can deviate from the standard age-based curve due to various factors. Hormonal contraception, particularly combined oral contraceptives, can temporarily suppress AMH readings by as much as 30%. This suppression is reversible, and AMH levels generally return to baseline shortly after the medication is discontinued.
Other medical conditions and interventions can cause a more permanent reduction. Ovarian surgery, such as procedures to treat endometriosis or remove cysts, can inadvertently damage surrounding ovarian tissue, leading to a direct loss of AMH-producing follicles. Exposure to chemotherapy or radiation treatments for cancer can also be highly toxic to the egg reserve, causing a significant and often permanent drop in AMH. Lifestyle factors like smoking have been consistently linked to lower AMH concentrations, suggesting an accelerated rate of ovarian aging. An AMH result must always be interpreted alongside a woman’s complete medical history.