You have likely heard of AMH — and maybe have even had your levels tested. But what is it exactly, and what does it have to do with your fertility? In this article, Dr. Sarah Zadek, ND, breaks it down.
What is AMH?
AMH stands for Anti-Mullerian Hormone and it’s made and released by the follicles in the ovaries. Each egg, or “oocyte,” in the ovary is surrounded by a layer of cells that are responsible for receiving hormone signals (like FSH–follicle stimulating hormone) and nutrients for the egg. Together, the oocyte and its surrounding cells are called a follicle.
A regular menstrual cycle can be broken down into phases:
- Menstruation (shedding of the uterine lining) and Follicular phase: the recruitment of follicles, followed by growth and maturation of the dominant follicle
- Ovulation: the dominant follicle is triggered (by a spike in luteinizing hormone, aka LH) to release its mature egg
- Luteal phase: the now empty follicle shell releases estrogen and progesterone which causes the uterine lining to thicken to prepare for embryo implantation. If an embryo doesn’t implant, the drop in estrogen and progesterone prompts menstruation, and the cycle continues.
It’s the small follicles in the ovaries that produce and release AMH.
What is AMH’s role in ovarian function?
AMH is produced by follicles in the early stages of growth–particularly “primary preantral” and small “antral” follicles (when they’re about 2-5mm). During the early follicular phase FSH is released from the pituitary gland and prompts a group of the small, AMH-making follicles to start producing a bit of estrogen, to suss out which one responds the best. One follicle will produce more estrogen than the others and that one becomes the “dominant follicle.”
Once this happens, AMH sends a signal to stop FSH. They don’t need it anymore now that their champion has been selected, so the rest of the smaller follicles can stop growing. Once the follicle grows larger than 6mm, AMH in that follicle also turns off since its job is done.
What’s the difference between AMH and antral follicle count (AFC)?
The term antral follicle count (AFC) refers to the number of follicles that are recruited from the primordial follicle pool, in the follicular phase. This amount generally reflects how many primordial follicles are left in that ovarian pool. As we age and our ovarian reserves become more depleted, our AFC will decline.
AFC and AMH are typically correlated (I say typically as sometimes there are anomalies). That means that at certain levels of AMH, we can estimate our functional egg reserves in the ovaries. Therefore, the older we become, the more we deplete the ovary’s egg reserves, and we see a drop in both AFC and AMH.
AMH and Fertility
AMH testing can be used as a marker of functional ovarian reserve (the approximate remaining supply of eggs in the ovaries). That said, it’s not going to give you a precise number of how many eggs or ovulatory cycles you have left, nor will it tell you how much time you have until you go through perimenopause or menopause. However, it does give us a rough idea on how responsive the follicles are as an indicator for when that process starts to slow down (ie. when the pool starts becoming depleted).
For these reasons, an AMH measurement can be used to help guide fertility decisions. For example, a low AMH may prompt you to start trying to conceive earlier, rather than wait too long. It can also help clinicians decide if IVF is the right route to go. If AMH and AFC are too low, IVF may not work as well, and other pre-treatments or recommendations may be made.
Low AMH and Fertility
Since AMH declines with age, we have different reference ranges for different age groups. AMH is typically most optimal from the ages of 25 to 30 years old, which is considered a time of “optimal” fertility. It then declines through our 30s, a time where fertility potential can still be good, while dropping significantly over the age of 40.
That said, there are cases where someone can have a relatively good AMH in their late 30’s, but it’s also possible to have a low AMH much earlier than expected; for example, in cases of premature ovarian insufficiency (POI).
Keep in mind that different clinics and labs may use different units for measuring AMH. Many labs use pmol/L, however, ng/mL can also be used. It’s very important to check the units next to your AMH to avoid panic. For example, 4.0ng/mL (which is about 28.0pmol/L) indicates optimal ovarian reserves, but 4.0pmol/L is low and indicates lower reserves.
High Levels of AMH
Does this mean that the higher the AMH the better? No, not necessarily. Having a high AMH is great up until a point. There is a range for what is considered “optimal” but going above and beyond that amount could indicate ovarian dysfunction.
When too much AMH is released it can cause a feedback signal. AMH is supposed to regulate follicle growth, like a gatekeeper, so high AMH can actually stop the growth of preantral follicles by turning off FSH too soon. This is more commonly found in people with PCOS (polycystic ovary syndrome). The “cysts” in PCOS aren’t typical or complex ovarian cysts, they’re actually ovarian follicles. So detecting an excessively high AMH can actually be an indicator of PCOS.
AMH and PCOS
The number of follicles recruited at the beginning of each cycle will be influenced by the total number of eggs/follicles in the ovarian reserve, but also by hormone signals like FSH. The pituitary gland releases FSH, which stimulates the recruitment and initial growth of follicles. FSH tells the follicle cells to turn androgens into estrogen (this is the initial growth sequence to help determine which follicle will become the dominant follicle).
In PCOS, we often see abnormal hormone levels, which feeds back to the pituitary gland (the master of FSH and LH hormones). High androgens, like testosterone, and/or high insulin, can tell the feedback loop to reduce FSH (high AMH will also do this), while interfering with LH. In the end, this leads to lots of little premature follicles that don’t always grow or mature properly (or on time), and abnormal LH release so ovulation timing is all over the place. Ovulation might occur on time, or it could be delayed significantly. This can result in:
- Long or irregular cycles. For example, only having a menstrual bleed every six week to six months (or longer)
- The inability to figure out when (or if) ovulation is taking place. This is most frustrating when trying to use LH test strips for identifying ovulation and the fertile window.
Testing your AMH
By testing for AMH, we can’t know for certain what your egg reserve is like, but it’s a really good screening test. If you’re flagged as having excessively high AMH levels, it could prompt further testing to find out if you have PCOS and if you’re ovulating.
Meanwhile, having low AMH can flag smaller follicle cohorts each cycle, and can prompt those women to start trying to conceive sooner, or speed up fertility treatments (including egg freezing). That said, it’s completely possible to have a low AMH and conceive naturally. Afterall, you just need one good egg (plus a sperm) to make a good embryo.
Does a high AMH mean my eggs are high quality?
No. Keep in mind that AMH only gives us an estimate of the amount of functional follicles in the ovaries. It can’t tell us anything about egg quality or ovulation. You can still get pregnant and have a healthy live birth even with a low for-age AMH. Similarly, you can have PCOS and high AMH levels, and still be able to get pregnant, just with a few extra challenges.
Egg quality typically refers to the health of an egg in terms of genetic material and cell function, including mitochondrial function–the organelle in our cells that makes ATP energy!
To date, there is no standard or known test to accurately measure egg quality. That said, if you’re undergoing an egg retrieval (either for egg freezing or IVF), we do have the ability to gather some information…
When eggs are matured and retrieved from the ovaries, an embryologist gets the opportunity to visually inspect each one. Upon examination, they can report any visual abnormalities. If those eggs are being used for IVF-ICSI, the embryologist might also report on the integrity of the egg membrane as they inject the sperm. If the eggs are instead going to be frozen, fertility and egg-freezing clinics may offer (for an additional cost) a MAGENTA™ or VIOLET™ report. These are AI-generated reports from individual pictures of each egg that is retrieved. The algorithm predicts the likelihood that a particular oocyte will lead to the formation of a mature embryo, that the embryo will contain the correct number of chromosomes, and the probability of it resulting in a live birth.
Keep in mind that these are predictions based on how normal or healthy the egg looks, but the results do not provide a guarantee. As well, we can’t discount the role of the sperm in embryo development! Therefore, it’s possible to gather some information on egg quality, but that information is limited and it requires actually looking at the oocyte, which isn’t helpful for those not undergoing IVF or egg freezing.
What can I do about egg quality?
Whether you’re trying to conceive naturally, preparing to freeze your eggs, or preparing for a treatment cycle like IUI or IVF, one of the best practices for egg quality is to focus on preconception health in the preceding three to four months. It takes about 100 days for a premature oocyte to fully mature, so this is the window to nurture and protect that cohort of follicles. At Conceive Health our preconception healthcare focuses on:
- Nutrients: helping you choose the right prenatal vitamins, and screening for nutrient deficiencies such as iron and vitamin D.
- DNA and cell protection: Reducing exposure to environmental pollutants and household chemicals; And managing oxidative stress and inflammation in the body.
- Optimizing your metabolic health: Supporting blood sugar and insulin regulation can have direct effects on the ovaries, while optimizing body composition can benefit hormone regulation and reduce inflammation.
- Diet support: Helping you develop and maintain healthy eating habits which affect all of the above!
- Stress support: Regulating the nervous system and cortisol can impact inflammation and reproductive hormones.
Book your free 15-minute discovery session today to learn more about how Conceive Health can help with your preconception health.
