Follicle Stimulating Hormone (FSH) is one of the most important hormones involved in the natural menstrual cycle as well as in pharmacological (drug-induced) stimulation of ovaries. It is the main hormone involved in producing mature eggs in the ovaries. Infertility affects approximately 15%- 20% of reproductive aged couples. The most commonly used biomarker test to assess ovarian reserve (OR) is the measurement of day 3 FSH; this test determines the level of FSH on day 3 of the menstrual cycle. Cycle day 3 is the preferred testing day due to the expected low level of estradiol, which in turn affects FSH levels via negative feedback control. Therefore, day 3 FSH levels would be expected to be low, a higher than normal day 3 FSH level would indicate a diminished ovarian reserve. By estimating the ovarian reserve, a prediction of the remaining reproductive lifetime could be assessed as well as the likely success of assisted reproductive techniques (ART) such as in vitro fertilization (IVF).
