Anti-Müllerian Hormone (AMH) is a protein hormone produced by the cells within the ovaries, offering a measurable glimpse into a woman’s reproductive potential. AMH testing provides a quantitative assessment of the remaining egg supply. Understanding the level of AMH in the bloodstream helps individuals and doctors make informed decisions about family planning and fertility treatments. The level reflects the overall size of the pool of developing follicles, but does not indicate whether a woman will become pregnant.
The Biological Role of Anti-Müllerian Hormone
AMH is secreted by the granulosa cells that surround and support the egg cells within the ovaries. Specifically, it is produced by the small, growing follicles in the preantral and early antral stages of development. The hormone belongs to the transforming growth factor-beta (TGF-β) superfamily and plays a regulatory role in folliculogenesis. Its presence acts to restrain the initial recruitment of primordial follicles from the resting pool, helping to manage the pace at which a woman’s finite egg supply is used.
The concentration of AMH in the blood directly correlates with the total number of these small, growing follicles present in the ovaries at any given time. Because the number of these growing follicles is proportional to the overall pool of resting primordial follicles, AMH serves as a reliable indirect marker for the size of a woman’s ovarian reserve. AMH levels reflect the quantity of eggs remaining, not the quality of those eggs.
Interpreting AMH Test Results and Ovarian Reserve
Ovarian reserve refers to the total number of healthy eggs remaining in the ovaries, and AMH is considered the best endocrine marker for assessing this reserve. The levels of AMH naturally decline throughout a woman’s reproductive years, mirroring the gradual depletion of the egg supply until levels become nearly undetectable around the time of menopause. This age-related decline begins in the late twenties, with the rate varying significantly among individuals.
A typical AMH level for a woman of reproductive age often falls between 1.0 and 4.0 nanograms per milliliter (ng/mL), though laboratories may use slightly different reference ranges. Levels considered favorable for a robust response to ovarian stimulation for fertility treatments are generally in the range of 1.0 to 3.5 ng/mL. A result above approximately 4.0 ng/mL is considered high and often suggests a larger-than-average follicular pool, which requires careful monitoring during treatments to prevent over-response.
Conversely, an AMH level below 1.0 ng/mL is commonly associated with a diminished ovarian reserve. Levels dropping below 0.5 ng/mL indicate a significantly low reserve and predict a challenging response, often resulting in fewer than three eggs retrieved during an assisted reproductive technology cycle. While a low AMH level suggests fewer eggs remain, it does not mean natural conception is impossible, as the hormone is a measure of quantity, not a definitive prediction of pregnancy success.
Clinical Applications of AMH Testing
Medical professionals use AMH testing to guide a number of clinical decisions related to reproductive health. One of the most established applications is in assisted reproductive technology, such as in vitro fertilization (IVF), where AMH is used to predict how the ovaries will respond to stimulation medications. The level helps in individualizing the dosage of follicle-stimulating hormone (FSH) to achieve an optimal number of eggs, minimizing the risk of a poor response or ovarian hyperstimulation syndrome (OHSS).
AMH testing also aids in assessing the potential timing of menopause, as the hormone’s decline precedes the final cessation of menstruation by several years. Tracking AMH over time can provide an estimate of a woman’s remaining reproductive lifespan, which can be valuable for family planning.
In the context of Polycystic Ovary Syndrome (PCOS), AMH is frequently used as a diagnostic aid. Women with PCOS often have AMH levels that are two to three times higher than those in healthy women of the same age, due to a large accumulation of small, AMH-producing follicles. The elevated AMH concentration is thought to contribute to the anovulation seen in PCOS by reducing the sensitivity of the follicles to FSH.
Factors Influencing AMH Levels
One of the key advantages of AMH testing is that its levels remain relatively consistent throughout the menstrual cycle, unlike other hormones like FSH, which fluctuate significantly. This stability means a blood sample can be drawn at any time, simplifying the testing process.
However, certain external factors and medical interventions can temporarily or permanently affect AMH readings. Long-term use of combined oral contraceptive pills (OCPs) is known to suppress AMH levels, with studies showing a temporary decrease of approximately 17-23%. This suppression is believed to be due to the OCPs inhibiting the growth of the small follicles, but the levels typically rebound after the medication is discontinued.
Ovarian surgery, such as the removal of an ovarian cyst or endometriosis, can directly damage the follicle-containing tissue and lead to a permanent reduction in AMH levels. Similarly, chemotherapy or radiation treatments for cancer can harm the ovarian reserve, and AMH testing is used both before and after such treatments to assess the extent of the damage.