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The Value of FSH Levels in Guiding Infertility Treatment
Louis N. Weckstein, M.D.
IVF and Medical Director
Reproductive Science Center of the Bay Area
Day 3 FSH Levels
Ovarian reserve, or relatively speaking, does a woman have a good number of eggs left in her ovaries, can be measured with a blood test. The FSH level is most useful when obtained on the second or third day of the menstrual cycle. In addition, measuring an estradiol level in the blood at the same time is helpful. FSH test results will fall into one of three ranges: normal, borderline, or abnormal. A normal day three FSH level is helpful with regard to a woman's ovarian reserve, however it is not completely predictive of a good response to fertility medication. A borderline day three FSH suggests somewhat poor ovarian reserve and the need for prompt, aggressive treatment. In this borderline situation, a short period of time may make a significant difference when using your own eggs. An abnormal FSH level suggests poor ovarian reserve and that the likelihood for a successful pregnancy (livebirth) with your own eggs is very low.The range for a normal FSH level varies from lab to lab depending on the type of assay used in that lab to measure FSH. This is of critical importance, since in one lab an FSH level of 12 may be considered normal, and in another lab it would fall into the abnormal range. Most infertility practices perform the blood testing in their facility and know precisely what the ranges are for normal, borderline, and abnormal FSH levels. Whereas many large independent labs (that many patients are forced to go to by their insurance if they want the testing to be covered) will state a normal range for FSH levels, but this range may be for all premenopausal women, and not be predictive of ovarian reserve in infertility patients.
In almost any lab, an FSH level under 10 is good and an FSH greater than 25 is clearly abnormal. In many infertility labs an FSH level of 10 - 15 is borderline as a predictor of ovarian reserve, and a level of greater than 15 is not good. However there are some labs in which an FSH level of 15 - 25 may be borderline. Once again it is critical that your physician interpret the levels based on the ranges known in their lab.
Estradiol Level
The estradiol level measured along with the FSH level on the second or third day of the cycle is also somewhat helpful. There is evidence that if the estradiol level at this time in the cycle is above 75, that even with a normal FSH level ovarian reserve is compromised. The estradiol level, however, does not seem to be as absolutely predictive as the FSH level.
Clomiphene Challenge Test
A further extension of the day three FSH level is the Clomiphene Challenge Test. This test seems to be more sensitive in picking up diminished ovarian reserve, particularly as women get over the age of 35. An FSH and estradiol level is measured on the third day of the cycle and then the medication clomiphene is taken, 100 mg on cycle days five through nine. An FSH level is then measured on day 10. If either the FSH level on cycle day 3 or 10 is abnormal, this suggests poor ovarian reserve. It seems as though the full Clomiphene Challenge Test is more important as women get closer to age 40. A greater number of infertility patients who are 40 years of age and older with a normal day three FSH and estradiol level will have an abnormal day 10 FSH level.
FSH Level Predictive Ability
Blood FSH levels vary from cycle to cycle, however it seems as though your ovarian response is predicted by your worst FSH level, so that even if the day three FSH level is normal following a prior month's abnormal FSH level, this is of poor prognosis.
In practical terms an abnormal FSH level usually, but not always predicts a poor response to fertility medication. More importantly it predicts a very low chance for a successful pregnancy when using fertility medication or in vitro fertilization. A study from the large IVF program at Saint Barnabas in New Jersey reported on the outcome of IVF cycles in more than 1000 patients with abnormal FSH levels (FSH > 14). The pregnancy rate with IVF in these patients was less than 3 percent and more than two thirds of these pregnancies miscarried, resulting in a delivery rate of less than 1 percent. Women who get pregnant with an elevated FSH level have a high likelihood of miscarrying. Some studies have suggested that an abnormal FSH level is associated with a high percentage of genetically abnormal embryos.
Other Tests
Studies are being done to evaluate other ways to test ovarian reserve. Possibilities include measurement of blood levels of Inhibin B, and ultrasound measurement of the number of small follicles on the ovaries early on in the cycle. However, not as much predictive information about these tests is currently available.
Age
Another factor of importance when considering fertility treatment options is the woman's age. Fertility and success rates with any fertility treatment are very much age related. Since livebirth rates from IVF in women who are over 43 years old are less than 5 percent, and probably less than 1 percent in women over the age of 45, these patients may want to consider oocyte donation even if they have normal FSH levels. On the other hand a woman who is 35 years old with a borderline FSH level would certainly want to consider a trial of IVF with her own eggs before moving on to egg donation. There is some evidence that pregnancy rates with IVF are good in younger women (under 35) even if they do not produce many eggs.
Making the Decision
It is important to note that abnormal FSH levels are not absolutely predictive of no possibility for a successful pregnancy. All of us in the field have had patients with markedly abnormal FSH levels who have gone on to deliver healthy babies. These situations are however, uncommon.
Certainly emotional issues and financial issues will also impact the decision of how to proceed with fertility treatment.
In summary, early cycle FSH levels (and the Clomiphene
Challenge Test) are useful tests to help guide patients how to proceed
with treatment. Borderline testing should suggest the need for prompt
treatment if using your own eggs. Abnormal results will provide
important (even if unwelcome) information about your chances of
having a successful pregnancy with infertility treatment, hopefully
saving time, money, and emotional trauma.
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