The assessment of a woman’s reproductive potential often begins with measuring specific hormones in the blood that reflect the state of her ovarian reserve. Ovarian reserve refers to the quantity of eggs remaining within the ovaries, which naturally declines over time. Two primary markers are used in this fertility assessment: Follicle-Stimulating Hormone (FSH) and Anti-Müllerian Hormone (AMH). Evaluating these hormones provides medical professionals with important insights into how the ovaries are functioning and responding to the body’s signals. These insights are crucial for individuals exploring their fertility status or planning assisted reproductive technologies.
Follicle-Stimulating Hormone: A Look at Ovarian Signaling
Follicle-Stimulating Hormone (FSH) is a protein hormone produced and released by the pituitary gland at the base of the brain. FSH stimulates the growth and development of ovarian follicles, the small sacs containing the eggs. FSH levels reflect the communication effort between the brain and the ovaries, acting as a direct signal in this hormonal axis.
Measuring FSH levels is typically performed on the third day (Cycle Day 3, or CD3) of the menstrual cycle to capture a baseline reading. This specific timing is necessary because FSH levels fluctuate significantly throughout the cycle. High FSH levels indicate that the pituitary gland is working harder to stimulate the ovaries, suggesting the ovarian reserve is diminished or less responsive.
Clinically, a consistently elevated baseline FSH level, often above 10 to 15 mIU/mL, indicates a reduced ovarian reserve. This higher concentration suggests that the remaining pool of follicles requires a greater hormonal push to initiate growth. FSH is limited as a standalone marker due to its dependence on precise cycle timing and inherent variability.
Anti-Müllerian Hormone: The Measure of Ovarian Reserve
Anti-Müllerian Hormone (AMH) is a protein hormone produced by the granulosa cells in small, growing follicles within the ovaries. AMH levels correlate closely with the size of the remaining pool of primordial and small antral follicles. AMH is considered a direct and quantitative measure of a woman’s ovarian reserve, reflecting the number of eggs remaining.
A major advantage of AMH testing is that its levels remain stable throughout the entire menstrual cycle. This stability means the test can be performed on any day, offering greater convenience and making it a more consistent measure than FSH. As ovarian reserve naturally declines with age, AMH levels decrease until they become virtually undetectable near menopause.
AMH provides an estimate of ovarian quantity, which is crucial for predicting a woman’s response to ovarian stimulation medications used in treatments like in vitro fertilization (IVF). Low AMH levels suggest a poor response to stimulation. High levels may indicate an increased risk of ovarian hyperstimulation syndrome (OHSS), making AMH important for personalizing treatment protocols.
Comparing Clinical Value: Which Hormone Provides the Clearest Picture?
When comparing FSH and AMH, most clinicians consider AMH the superior single marker for assessing ovarian reserve and predicting ovarian response in IVF. AMH directly measures the product of the small, growing follicles, providing a consistent estimate of egg quantity. Its cycle-independent stability removes the variability that plagues FSH testing, making the results easier to interpret.
AMH is significantly better at predicting the number of eggs retrieved during an IVF cycle, which is a major factor in treatment planning. Studies show that AMH is a more accurate predictor of IVF success than FSH, especially when hormone levels are discordant. A reassuring AMH level, even with elevated FSH, often suggests a better clinical outcome.
FSH still provides important complementary information: insight into the hormonal signaling axis. Elevated FSH levels demonstrate the body’s increased effort to overcome the reduced responsiveness of the ovaries, reflecting a change in the pituitary-ovarian feedback loop. FSH is often the first marker to rise as a woman approaches menopause, offering a measure of the system’s overall function.
Fertility specialists rarely rely on a single test, opting instead for a comprehensive approach. This includes both hormones and factors like the patient’s age and an antral follicle count (AFC) via ultrasound. While AMH is favored for estimating egg quantity and predicting treatment response, FSH provides valuable context about the hormonal communication system.