What is AMH and Why Does it Decline?
Anti-Müllerian Hormone (AMH) is a protein hormone produced by the granulosa cells of the small, pre-antral and antral follicles within the ovaries. It is considered a reliable marker for a woman's ovarian reserve, or the total number of eggs she has left. A woman is born with a finite number of eggs, and this number naturally decreases over her lifetime through a process called atresia. As the ovarian follicle pool diminishes with age, so do the levels of AMH.
This continuous decline is a normal part of reproductive aging, culminating in menopause when AMH levels become virtually undetectable. However, the speed of this decline is not a constant, uniform process for every woman. It fluctuates and can be influenced by multiple factors, making individual interpretation crucial.
The Average Annual Rate of AMH Decline
Numerous studies have investigated the age-related decline of AMH. A key study involving over 17,000 women found that the median serum AMH value had an average yearly decrease of 0.2 ng/mL through age 35. Following this period, the rate of decline diminished to about 0.1 ng/mL/year after age 35. Other research, while showing similar trends, noted slightly different rates; for instance, one study found an average yearly decrease of 0.27 ng/mL through age 35, decreasing to 0.12 ng/mL afterward.
It is important to remember that these are average or median figures. The rate of decline can vary significantly between individuals. While the overall trend is clear, a woman's AMH level can also fluctuate slightly from one measurement to the next due to various factors, including the testing assay used.
Factors that Influence the Speed of AMH Decline
While age is the most significant factor affecting AMH levels, other variables can accelerate or potentially mitigate the rate of decline. These include:
- Genetics: An individual's genetic predisposition can play a role in the initial size of the ovarian reserve and the rate of its depletion.
- Lifestyle Choices: Smoking, excessive alcohol consumption, and a poor diet have been associated with lower AMH levels and a potentially faster decline. Conversely, a diet rich in antioxidants, healthy fats, and Vitamin D may support ovarian health.
- Medical Conditions and Procedures: Conditions like polycystic ovary syndrome (PCOS) can be associated with higher AMH levels and a slower rate of decline. Conversely, treatments involving more than three controlled ovarian hyperstimulation (COH) cycles or certain adnexal surgeries can accelerate the decline in infertile women.
- Stress: High and prolonged stress levels can negatively impact hormonal balance, which may affect ovarian function.
- Environmental Factors: Exposure to certain environmental toxins and pollutants has been linked to a decline in fertility.
AMH Levels by Age: A Comparison
To illustrate the typical decline, the following table presents median AMH levels across different age groups, derived from various studies. It is critical to understand that these figures are general guidelines, and significant individual variation exists. Lab testing methods can also produce different results.
| Age Group | Median AMH Level (ng/mL) | Interpretation |
|---|---|---|
| Under 30 | ~2.90 | Higher ovarian reserve |
| 30–34 | ~2.40 | Healthy range for age |
| 35–37 | ~2.00 | Normal for this age, but declining |
| 38–40 | ~1.50 | Lower ovarian reserve |
| 40+ | Often <1.0 | Significantly reduced ovarian reserve |
The Role of AMH in Fertility and Treatment
An AMH test provides an assessment of ovarian quantity, not egg quality. Therefore, a low AMH level does not mean conception is impossible, but it does indicate a reduced number of remaining follicles. For women undergoing assisted reproductive technology (ART) like IVF, AMH levels are a valuable tool for predicting the ovarian response to stimulation medication. However, a single AMH reading is not recommended for counseling women on their general reproductive status or predicting time to pregnancy if they are not infertile. A comprehensive evaluation includes a combination of factors, such as age, FSH levels, and antral follicle count (AFC).
For those with low AMH, fertility treatments can be customized to maximize the chances of success, potentially including adjusted medication protocols. While there is no definitive way to reverse or significantly increase AMH levels, lifestyle adjustments and sometimes supplements like DHEA and CoQ10 may help support overall ovarian health. For more information on fertility planning and treatment, consult reliable sources like the American Society for Reproductive Medicine.
Conclusion
AMH levels naturally decline with age, with the steepest decline generally occurring in the late 20s and early 30s. The rate of reduction slows after age 35, but the overall number of follicles continues to decrease. While average annual decline rates provide a general picture, individual experiences vary widely due to genetics, lifestyle, and medical history. AMH testing serves as a useful tool for assessing ovarian reserve, particularly in the context of fertility treatments like IVF. By understanding the factors that influence AMH and adopting a proactive approach to reproductive health, women can make more informed decisions about their fertility journey. Ultimately, AMH provides a valuable snapshot, but it should always be interpreted in conjunction with other clinical and personal health factors. This comprehensive view is key to navigating the complex landscape of reproductive aging.
