What is AMH?

Anti-Müllerian Hormone (AMH) is produced by granulosa cells in ovarian follicles, beginning in the primary follicles that develop from the primordial follicle stage, which are microscopic and not visible via ultrasound. AMH production peaks during the pre-antral and early antral stages (under 4mm in diameter) of follicle development, and diminishes significantly in larger follicles over 8mm. Because AMH levels remain relatively stable, testing can be conducted at any point during a woman's menstrual cycle.

How AMH Levels Assess Fertility

As AMH is solely produced by small ovarian follicles, blood levels of this hormone serve as an indicator of the pool of growing follicles in women. Research indicates that the size of this pool is largely influenced by the number of remaining primordial follicles, which are in a dormant state. Consequently, AMH levels are thought to reflect a woman's ovarian reserve, or the remaining egg supply.

With advancing age, the number of primordial follicles declines, leading to decreased AMH levels and fewer visible antral follicles on ultrasound. Women with a higher number of small follicles, such as those with polycystic ovarian syndrome (PCOS), typically exhibit elevated AMH levels. In contrast, women approaching menopause tend to have lower AMH levels.

AMH Levels and IVF Success Rates

Higher AMH levels are associated with a better response to ovarian stimulation during in vitro fertilization (IVF), resulting in more eggs being retrieved and increasing the likelihood of a successful pregnancy. Although AMH levels do not necessarily indicate egg quality, having more eggs available improves the chances of obtaining at least one high-quality embryo for transfer.

Research by fertility specialists has shown that:

- High AMH levels correlate with lower cancellation rates, increased egg retrieval, and higher live birth rates, as well as a greater chance of having leftover embryos for freezing.
- Low AMH levels alone do not predict diminished IVF success in women under 35.
- Couples should not be discouraged from pursuing IVF solely based on low AMH values, as live birth rates remain reasonable in these cases.

Normal AMH Levels

The interpretation of AMH levels can vary, and while the test is gaining acceptance, agreed-upon normal ranges are still being established. The following guidelines reflect common interpretations based on fertility literature:

- High (often in PCOS): Over 4.0 ng/ml
- Normal: 1.5 – 4.0 ng/ml
- Low Normal Range: 1.0 – 1.5 ng/ml
- Low: 0.5 – 1.0 ng/ml
- Very Low: Under 0.5 ng/ml

It's important to understand that AMH levels represent a continuum; small variations may not significantly impact fertility potential.

Ovarian Reserve Testing Methods

AMH is one of several tests used to evaluate ovarian reserve. 

Each test has its limitations, so fertility specialists often use a combination of assessments to estimate the remaining egg supply accurately.


(Note: AMH has also been referred to historically as “Müllerian inhibiting substance” or MIS.)