Anti-Mullerian Hormone (AMH) plays a vital role in foetal development, as well as having other important functions in the mature adult. At about eight weeks of development, the human foetus features two sets of ducts. One of them has the potential to develop into a male baby, the other carrying the potential for a female. If the foetus has X and Y chromosomes, making it genetically male, it produces the anti-Mullerian hormone, triggering the disappearance of the female ducts. Mullerian means female, hence the name anti-Mullerian. Testosterone is produced, causing the survival of the male (Wollfian) ducts which go on to become the male reproductive system. In a genetically female foetus with two X chromosomes, the lack of testosterone causes the disappearance of the Wollfian ducts and the Mullerian ducts develop into the female reproductive system.
So much for the historical-biological context. Anti-Mullerian hormone levels also play a crucial role in how we can measure fertility in the adult female, in the anti-Mullerian hormone test.
What do anti-Mullerian hormone levels mean?
Your ovaries at birth contain all the follicles (immature egg sacs) that they will ever have, and the number of these declines gradually with age. This is one of the reasons for the well-known decline in female fertility after the age of around 35. These follicles secrete anti-Mullerian hormone (AMH) as they develop. The hormone circulates throughout the body in the blood system. It is therefore a relatively simple task to measure the amount of AMH circulating in the body by means of a blood test. The hormone level provides a useful indicator (though not an exact count) of the number of eggs remaining in your ovarian reserve.
What is the anti-Mullerian hormone test?
All follicles produce a certain level of AMH. They start out as primordial follicles which are too small to be seen with the naked eye. However, every month a number of follicles respond to hormonal signals and start to develop, with only one becoming the one which will eventually reach full maturity and be ovulated. One of the stages of development is when the follicles acquire a fluid-filled cavity known as the antrum. These are hence known as antral follicles. The antral follicles excrete even higher levels of AMH. These allow the anti-Mullerian hormone blood test to provide a fairly reliable assessment of your overall ovarian reserve.
Further testing for the full fertility picture
At this stage of their development, the antral follicles measure between 2 mm and 10 mm. They can therefore be seen on an ultrasound scan, providing a further confirmation, along with the anti-Mullerian hormone test, of the probable ovarian reserve. The ultrasound scan is undertaken by using a transvaginal probe, which means that the fertility specialist can ‘see’ the developing follicles in your ovaries.
For the statistically-minded, here are some more numbers to show what the antral follicle count (AFC) means for your fertility:
If your antral follicle count is very low, it does not necessarily mean that you are unable to get pregnant. It means that you are unlikely to respond well to fertility treatment such as IVF in which the ovaries are stimulated with hormonal medication to produce multiple eggs. In addition, women with a very low antral follicle count before the age of 40 could be diagnosed with premature ovarian failure, often referred to as premature menopause.
What are normal levels of AMH?
For those who like to understand what the number signifies, here is an approximate guide to normal levels of AMH. The AMH can be measured in two different units: picomoles per litre (pmol/L) or nanograms per millilitre (ng/mL). When measured in ng/mL, the measure is simple: any level over 1ng/mL shows a normal level of ovarian reserve. When measured in pmol/L normal levels are within the following ranges:
- Age 20 – 29 years, 13.1 – 53.8
- Age 30 – 34 years, 6.8 – 47.8
- Age 35 – 39 years, 5.5 – 37.4
- Age 40 – 44 years, 0.7 – 21.2
- Age 45 – 50 years, 0.3 – 14.7
To further put these numbers into context, a level of under 4.9 indicates a level of fertility that is very low or undetectable. Levels of between 4.9 and 16.2 indicate low fertility, and a measure greater than 16.2 shows a normal level of fertility.
Why should you have an anti-Mullerian hormone test?
Getting an AMH test can be a very useful step for young women thinking about when is the right time to start a family. For those who, like many others, want to get on with consolidating career, financial and emotional stability before embarking on a family, evidence that they have a good ovarian reserve will provide reassurance. On the other hand, an early warning that fertility is declining more rapidly than expected could have an important bearing on future planning.
We all know that fertility declines with age, but it is not possible to predict the rate of this decline for any single individual. Many people assume that since their periods are regular, their fertility will be fine, but this is not always the case. If the results from the test show normal fertility, all well and good. Anyway, it’s wise to have a repeat test each year so that you have an early warning system in place. If your AMH levels are low, it could be time to re-assess your priorities and listen to the ticking of the body clock.
Getting a fertility diagnosis with IVI
When you attend a fertility clinic for a fertility assessment, both methods of checking your ovarian reserve, the blood test and the ultrasound scan, will probably be used to increase the accuracy of diagnosis.
For a check on the current status of your fertility, or for any other fertility concerns you may have, you can find your nearest IVI clinic through our website which provides full address, telephone and map details. Or you could simply fill in our online contact form and we’ll get right back to you.