Anti-Müllerian Hormone (AMH) is a protein hormone produced by granulosa cells within the small follicles of the ovaries. These follicles are tiny fluid-filled sacs that contain immature eggs. Measuring AMH levels in the blood provides an estimate of a woman’s ovarian reserve, reflecting the number of eggs remaining.
A low AMH level indicates a diminished ovarian reserve. While a natural decline in AMH is an expected part of aging, various other factors can also contribute to lower levels. This decline does not necessarily mean infertility, but it can impact fertility planning.
The Impact of Age
Age is the most significant factor influencing Anti-Müllerian Hormone levels. AMH concentrations naturally change throughout a woman’s life, reflecting ovarian aging. From birth, a woman has a finite number of eggs, which are gradually depleted over time.
AMH levels typically increase from birth, reaching a plateau around 25 years of age. After this peak, AMH begins a steady decline, eventually becoming undetectable as a woman approaches menopause. This age-related decrease in AMH directly mirrors the natural reduction in ovarian follicles.
The depletion of ovarian follicles occurs due to natural loss and monthly recruitment of eggs for ovulation. As the number of available follicles decreases, so does the production of AMH. This physiological process explains why AMH levels are generally lower in older women.
Medical Conditions and Treatments
Several medical conditions and treatments can negatively affect ovarian reserve and AMH levels. Endometriosis, a condition where tissue similar to the uterine lining grows outside the uterus, is one such factor. Women with endometriosis often exhibit lower AMH levels.
Ovarian endometriomas, a type of ovarian cyst associated with endometriosis, can impact ovarian structure and function. Surgical removal of these cysts, especially endometriomas, can lead to a significant reduction in AMH levels. The decline can be more pronounced after bilateral surgery or procedures that affect ovarian blood supply.
Autoimmune diseases, such as premature ovarian insufficiency (POI), also known as primary ovarian insufficiency, contribute to low AMH. POI is characterized by the loss of normal ovarian function before age 40. In such cases, AMH levels are typically very low or undetectable.
Cancer treatments like chemotherapy and radiation therapy are known to damage ovarian follicles. These gonadotoxic treatments can significantly reduce a woman’s ovarian reserve, leading to a substantial drop in AMH levels. The extent of this decline often depends on the type and intensity of the treatment.
Lifestyle and Environmental Factors
Certain lifestyle choices and environmental exposures can also lower AMH levels. Smoking, for instance, is strongly associated with decreased AMH. Nicotine and other toxins in cigarette smoke can directly harm ovarian follicles, accelerating their depletion.
Current smokers often have lower AMH values, which may contribute to an earlier onset of menopause. The toxic effects of smoking on ovarian health are evident.
Exposure to environmental toxins can also negatively impact ovarian reserve. Combustion by-products, such as those from burning wood or artificial firelogs indoors, have been linked to lower AMH levels. Other industrial chemicals and endocrine disruptors may also contribute to ovarian damage.
Poor diet, high stress levels, and obesity can influence AMH. These elements may create an unfavorable environment for ovarian health.
Genetic Predisposition
Some individuals have a genetic predisposition to lower AMH levels or earlier ovarian aging. Genetic variations can influence the initial size of a woman’s ovarian follicle pool or the rate at which follicles deplete.
A family history of early menopause can indicate such a genetic predisposition. Research continues to identify specific genes, such as FMR1 and BRCA1/2, that may play a role in determining ovarian reserve and the timing of ovarian aging. These genetic factors can lead to diminished ovarian reserve even in younger women.