Anti-Müllerian Hormone as a Marker of Ovarian Reserve
Anti-Müllerian hormone (AMH) is the best currently available hormonal measure of ovarian reserve, accurately reflecting the pool of growing follicles in the ovary and serving as a reliable indicator of functional ovarian reserve. 1
What AMH Measures
AMH is produced exclusively by granulosa cells of small, growing ovarian follicles in the ovary. 1, 2 The key physiological role of AMH is to:
- Inhibit recruitment of primordial follicles into the growing pool at initial recruitment 3
- Lower FSH-sensitivity of follicles at cyclic recruitment, acting as a follicular gatekeeper that limits follicle growth initiation 3, 4
- Correlate strongly with the number of antral follicles, making it quantitatively reflective of the functional ovarian reserve 1, 3
Why AMH is Superior to Other Markers
AMH is superior to age, basal FSH, estradiol, and inhibin B for assessing ovarian reserve in healthy women. 1 The advantages include:
- Does not vary significantly by menstrual cycle day, allowing convenient testing at any time 5, 1
- Not affected by exogenous estrogen or progesterone, unlike FSH which requires cycle-specific timing 5, 1
- FSH remains a late marker of ovarian dysfunction and is less sensitive than AMH for early detection of diminished ovarian reserve 1, 6
Clinical Interpretation
Very low AMH levels (below 0.7 ng/mL) indicate ovarian failure or severely diminished ovarian reserve. 1 However, important caveats exist:
- AMH reflects the "functional ovarian reserve" (the pool of growing follicles responsive to gonadotropins) rather than the total primordial follicle pool 1, 2
- AMH only measures FSH-dependent follicles, not the underlying primordial pool, as demonstrated in cases where AMH increases with gonadotropin stimulation 7
- AMH assays lack international standardization, so results must be interpreted using laboratory-specific reference ranges 1, 2
Age-Specific Considerations
The reliability of AMH varies significantly by age:
- For women ≥25 years: AMH is inversely correlated with increasing age and provides reliable information about remaining reproductive lifespan 1, 6, 8
- For women <25 years: AMH interpretation is less reliable due to potential fluctuations throughout the menstrual cycle, and antral follicle count by transvaginal ultrasound remains the gold standard 1, 6, 8
- AMH peaks at approximately age 25 years in the general population, and there is no evidence that low AMH indicates reduced fertility in females under 25 years 5
Special Populations
In cancer survivors treated with alkylating agents and/or radiotherapy, AMH shows promise as a predictor of ovarian reserve and timing of onset of menopause. 5, 6 Key findings include:
- AMH levels are decreased in both adult and pediatric cancer patients, with potential recovery after low doses of alkylating chemotherapy 5
- AMH may identify women at risk for premature ovarian insufficiency (POI), though it is not part of the formal definition of POI 5, 6
- Neither AFC nor AMH are part of the diagnostic criteria for POI, as FSH and estradiol remain the standard for diagnosis, but AMH may predict early decrease in ovarian reserve before FSH becomes abnormal 5
Common Pitfalls
- Do not use AMH routinely for preconception counseling in young, fertile women under 25 years due to limited predictive value and potential fluctuations 8
- AMH testing is more tempered (may be reasonable) and limited to women ≥25 years where validated normative data are available 5
- Direct comparison of results between different AMH assays remains problematic due to lack of international standardization 6, 2
- AMH levels can fluctuate during the menstrual cycle, particularly in young women, questioning its absolute stability 6, 7