What is AMH?
AMH, or anti-mullerian hormone is a substance that is produced by granulosa cells in ovarian follicles. It is first made in primary follicles after they advance from the primordial follicle stage. At these stages the follicles are microscopic in size and can not be seen by ultrasound. Anti mullerian hormone has also been referred to (mostly in the past) as "mullerian inhibiting substance", or MIS.
AMH production is highest in the preantral and small antral stages (less than 4mm diameter) of follicle development. Production decreases and then stops as the follicles grow larger. There is almost no AMH made in human follicles over 8mm in size. Because of this, the levels are quite constant and the AMH test can be done on any day of a woman's cycle.
AMH and fertility
How can AMH hormone levels be a fertility test?
Since AMH is produced only in small ovarian follicles, blood levels of this substance have been used to attempt to measure the size of the pool of growing follicles in women.
Research shows that the size of the pool of growing follicles is heavily influenced by the size of the pool of remaining primordial follicles (microscopic follicles in "deep sleep"). Therefore, AMH blood levels are thought to reflect the size of the remaining egg supply - or ovarian reserve.
With increasing female age the size of their pool of remaining microscopic follicles decreases. Likewise, their blood AMH levels and the number of ovarian antral follicles visible on ultrasound also decreases.
Women with many small follicles, such as those with polycystic ovaries have high AMH hormone values and women that have few remaining follicles and those that are close to menopause have low anti-mullerian hormone levels.
AMH levels and pregnancy chances with in vitro fertilization
Women with higher AMH values will tend to have better response to ovarian stimulation for IVF and have more eggs retrieved. In general, having more eggs with IVF gives a higher success rate. We do not have a lot of data yet on what to tell couples going through IVF about their AMH results and chances for conception. However, the table below shows ranges for AMH levels and some information about interpretation.
AMH levels probably do not reflect egg quality, but having more eggs at egg retrieval gives us more to work with - so we are more likely to have at least one high quality embryo available for transfer back to the female partner's uterus.
What is a normal AMH level?
Interpretation of anti-mullerian hormone levels and chances for conception
There are some problems involved with interpretation of AMH hormone levels. Because the test has not been in routine use for many years, the levels considered to be "normal" are not yet clarified and agreed on by the experts. Also, not all current commercial assays give equivalent results.
The table below has AMH interpretation guidelines from the fertility literature and our own experience. Do not get carried away with the cutoff values shown here. For example, the difference between a 0.6 and a 0.7 ng/ml test result puts a woman in a "different box" in this table - but there is very little real difference in fertility potential. In reality, it is a continuum - and not something that categorizes well.
Interpretation of AMH Blood Level
- High (often PCOS): Over 3.0 ng/ml
- Normal: Over 1.0 ng/ml
- Low Normal Range: 0.7 - 0.9 ng/ml
- Low: 0.3 - 0.6 ng/ml
- Very Low: Less than 0.3 ng/ml
More will be learned regarding anti-mullerian hormone levels and outcomes as we continue to use the AMH fertility test and study the relationship between AMH hormone values and fertility, ovarian responsiveness, chances for IVF success, etc.
Ovarian reserve testing methods
Anti mullerian hormone is one potential test of ovarian reserve. There are several more tests that are currently used for evaluation of the remaining egg supply. None of the tests are perfect, and fertility specialists will often use a combination of tests to try to get a better estimate of the size of the remaining egg supply.
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