Evaluation of ovarian function – ovarian reserve
Ovarian reserve is the capacity of the ovaries to respond to stimulation. It is a parameter that evaluates the number of oocytes that may result from ovarian stimulation.
The parameter associated with the oocyte quality is the woman’s age.
Diagnostic tests available for assessing ovarian reserve provide indirect information. An accurate diagnosis may only be made after an actual ovarian stimulation cycle.
The following techniques are available to assess ovarian reserve:
A transvaginal ultrasound allows for the measurement of follicles during the initial phase of the cycle (follicular phase). These follicles measure between 2-8 mm and represent the number of follicles that may mature during a typical stimulation protocol.
There is no consensus on the number of follicles that is considered ideal for a good response to hormonal stimulation. A large number of follicles (eg > 15) increases the risk of hyperstimulation, whereas a low number (eg <3) indicates possible poor ovarian response. Therefore, it is up to the Gynaecologist to choose the appropriate drug dose and treatment regimen, while the couple is kept informed regarding the number of oocytes that are expected to be collected. FSH levels
FSH (follicle stimulating hormone), synthesized and secreted by the anterior pituitary gland, acts on the ovaries and promotes growth of the ovarian follicles. Its measurement during the follicular phase reflects the ability of ovaries to produce oocytes during stimulation. High levels of FSH (ie > 10 mIU) usually indicate low response to ovarian stimulation.
FSH levels may vary from cycle to cycle, but the prognosis is usually characterized by the highest measurement.
Antimullerian Hormone (AMH)
AMH is important for two reasons: 1) it regulates the number of available follicles and 2) it allows the development of a single follicle per natural cycle, as it reduces the follicles’ sensitivity to FSH.
Along with ultrasound measurement of ovarian follicles (Antral Follicle Count, AFH), AMH is considered the most reliable indicator of ovarian reserve.
The team of Fertility Specialists at EmbryoClinic has carried out extended research on AMH levels within IVF cycles.
The results of the research were published in the medical journal “Human Fertility 2011” and won an award at the 9th International Scientific Meeting of the Royal College of Obstetricians and Gynaecologists in Athens, 2011.
In some cases, together with ovarian aging, there is a shortening in the duration of the menstrual cycle. This may lead to high levels estradiol, during the follicular phase, associated with low ovarian response. Usually, estradiol levels are evaluated together with those of FSH on Days 2 to 4 of the cycle.
This hormone is produced by small follicles during the first half of the follicular phase. Low levels of inhibin B are associated with reduced ovarian reserve.
However, the clinical application of inhibin B monitoring is limited, since it does not exceed the prognostic value of other indicators such as AMH and AFC.