AMH, or Anti-Müllerian Hormone, is a widely discussed biological marker used in fertility planning. It offers a unique snapshot of a person’s reproductive status. Understanding AMH and what its measurement reveals is crucial for assessing ovarian function and the quantity of a person’s egg supply.
Anti-Müllerian Hormone Defined
AMH is a glycoprotein belonging to the transforming growth factor-beta superfamily of signaling proteins. Its fundamental function occurs during early fetal development, playing a decisive role in sex differentiation. In male fetuses, AMH is produced by the Sertoli cells in the developing testes to cause the regression of the Müllerian ducts.
The Müllerian ducts would otherwise develop into internal female reproductive organs, such as the uterus, fallopian tubes, and the upper part of the vagina. In the absence of high AMH levels, which is the case in female fetuses, these ducts are allowed to develop into the female reproductive tract. In adults, AMH is produced by the granulosa cells that surround the eggs within the ovarian follicles.
AMH as a Measure of Ovarian Reserve
In adult females, the primary clinical relevance of AMH is its use as a measure of the functional ovarian reserve, the estimated number of eggs remaining in the ovaries. The hormone is secreted by the granulosa cells of the small, growing follicles, specifically those in the pre-antral and small antral stages. These small follicles are continuously recruited from the larger pool of resting follicles, making the AMH level an indirect reflection of the total remaining supply.
A higher AMH level generally correlates with a larger number of these small, growing follicles and, consequently, a greater ovarian reserve. Conversely, a lower AMH level suggests a diminished reserve, indicating a smaller remaining pool of follicles. AMH is considered an effective marker because its concentration remains relatively stable throughout the menstrual cycle, unlike other reproductive hormones. The measurement provides a quantitative assessment of the egg supply, which helps healthcare providers estimate a person’s reproductive timeline and potential response to fertility treatments.
Understanding and Interpreting AMH Test Levels
The AMH test is a simple blood test that can be performed at any time without special preparation, and the resulting level is typically reported in nanograms per milliliter (ng/mL). For women in their reproductive years, an AMH level between 1.0 and 3.0 ng/mL is often considered to be within the average range. Levels below 1.0 ng/mL are generally classified as low and may indicate a diminished ovarian reserve.
A low AMH result may prompt discussions about trying to conceive sooner or considering fertility preservation options, such as egg freezing. However, a low AMH level alone does not predict an inability to conceive naturally, as successful pregnancy depends on many factors. Levels above 3.5 ng/mL are often considered high. This elevated level is frequently associated with conditions like Polycystic Ovary Syndrome (PCOS), where an excess number of small follicles accumulate in the ovaries.
AMH is a measure of egg quantity, but it does not indicate egg quality. Egg quality remains the most significant factor for achieving a healthy pregnancy, and it is primarily determined by the person’s age. Therefore, AMH levels are most useful when combined with other fertility assessments, such as an antral follicle count (AFC) via ultrasound, to provide a complete picture of reproductive health.
Factors That Influence AMH Results
While AMH levels naturally decline with age as the follicle pool is depleted, several other factors can temporarily or chronically influence the test result. One significant variable is the use of hormonal contraceptives. Hormonal birth control can temporarily suppress AMH levels, sometimes by as much as 20% to 30%, which can lead to an artificially low reading.
The effect of hormonal contraceptives is reversible, with AMH levels returning to their baseline range after the medication is discontinued. Conversely, Polycystic Ovary Syndrome causes consistently high AMH levels due to the presence of numerous small, arrested follicles that actively secrete the hormone. Other variables, such as a history of ovarian surgery, chemotherapy, or vitamin D deficiency, can also influence AMH concentration. These influences underscore the importance of interpreting the AMH result within the context of a person’s medical history and current medications.