FSH- Known as the Follicular Stimulating Hormone.
How is it used?
FSH is often used in conjunction with other tests (LH, testosterone, estradiol, and progesterone) in the workup of infertility in both men and women. FSH levels are used to help determine the reason a man has a low sperm count. FSH levels are also useful in the investigation of menstrual irregularities and to aid in the diagnosis of pituitary disorders or diseases involving the ovaries or testes. In children, FSH and LH are used to diagnose delayed or precocious (early) puberty.
When is it ordered?
FSH may be ordered when a woman’s menstrual cycle has stopped or become irregular, to determine if the woman has entered menopause.
What does FSH hormone do?
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 the ovaries. It is the main hormone involved in producing mature eggs in the ovaries. FSH is the same hormone that is contained in the injectable gonadotropins which are used to produce multiple eggs for infertility treatment.
What produces FSH hormone?
Both FSH and LH hormone are produced by the pituitary gland at the base of the brain. When a women goes into menopause she is running out of eggs in her ovaries. The brain senses that there is a low estrogen environment – and signals the pituitary to make more FSH hormone. More FSH is released from the pituitary in an attempt to stimulate the ovaries to produce a good follicle and estrogen hormone.Think of it like stepping on the gas pedal in the car to get going. The FSH is the gas, and the pituitary gland releases FSH to get a follicle “going” at the beginning of every menstrual cycle. If there are less follicles left (and perhaps lower quality follicles) the amount of “gas” has to be increased to get a follicle developing.
In a menopausal woman, the gas pedal is on the floor for the rest of her life – even though there are no follicles (or eggs) left. The woman’s body never gives up trying – FSH levels are permanently elevated.
Women in menopause have high FSH hormone levels – above 40 mIU/ml. As women approach menopause their baseline FSH levels (day 3 of their cycle) will tend to gradually increase over the years. When they run out of follicles capable of responding, their FSH will be high and they stop having periods.
Is there anything else I should know?
FSH results can be increased with use of cimetidine, clomiphene, digitalis, and levodopa. FSH results can decrease with oral contraceptives, phenothiazines, and hormone treatments. FSH has been reported to increase with age and in smokers.
A recent nuclear medicine scan may interfere with results of the FSH test.
Using FSH for fertility testing.
Why do we measure the FSH level on day 3?
By measuring a woman’s baseline FSH on day 3 of the cycle (we do it on day 2, 3, or 4), we get an indication as to whether she has normal “ovarian reserve”. We are looking at how hard her body needs to “step on the gas” early in the menstrual cycle to get a follicle growing.
Therefore, if the baseline FSH is elevated the ovarian reserve (how many eggs are left) is reduced (sometimes the egg quality is also reduced).
Some practical problems with the day 3 FSH test:
- The cut off values used to say that egg quantity is good, OK, or poor is laboratory dependent. For example, and FSH of 11 in one laboratory may reflect good ovarian reserve – whereas a level of 11 in another lab using a different assay may indicate diminished ovarian reserve. See below for more.
- While an abnormal result (high baseline FSH) tends to be very predictive of low egg quantity, a normal result does not necessarily mean that the egg quantity is good. There are a significant number of women with normal FSH values that have a reduced egg supply. The lower egg supply is not being reflected in their FSH value. This is why doing antral follicle counts and AMH levels can be useful. By doing multiple ovarian reserve tests, we are more likely to find an ovarian reserve problem if there is one.
This is particularly true for women in their 40s. An infertile 44 year old woman with a normal FSH (for example 6) still has a very low probability of conceiving and delivering a baby with in vitro fertilization – or with any other fertility treatment. The fact that she is 44 greatly diminishes her chances – even if her FSH is normal. This is why IVF programs have age cutoffs.
The oldest women accepted by IVF programs varies somewhat – most programs have a cutoff somewhere between age 42-45. Infertile women older than 44 will very rarely be successful using their own eggs. However, these women are excellent candidates for in vitro fertilization with donor eggs.
Interpreting day 3 FSH blood test results – what are normal FSH levels?
In our fertility center we currently use an assay made by DPC that is run on an Immulite machine. We consider normal FSH level to be anything less than 9. As levels go above 9 we often see a reduction in response to ovarian stimulating drugs – as described in the table below.
If your FSH levels were run using a different assay, you can not compare your results to those shown below with confidence. For example, with some assays an FSH of 12 is normal.
|Day 3 FSH level||FSH interpretation for DPC Immulite assay|
|Less than 9||Normal FSH level. Expect a good response to ovarian stimulation.|
|9 – 11||Fair. Response is between normal and somewhat reduced (response varies widely). Overall, a slightly reduced live birth rate.|
|11- 15||Reduced ovarian reserve. Expect a reduced response to stimulation and some reduction in embryo quality with IVF. Reduced live birth rates on the average.|
|15 – 20||Expect a more marked reduction in response to stimulation and usually a further reduction in embryo quality. Low live birth rates. Antral follicle count is an important variable.|
|Over 20||This is pretty much a “no go” level in our center. Very poor (or no) response to stimulation. “No go” levels should be individualized for the particular lab assay and IVF center.|
More issues regarding day 3 FSH testing
In general, your ovarian reserve is as bad as your worst FSH. If you have an FSH of 15 in one cycle and then a a 7 in another cycle – the situation is not improving. Some women “bounce around” with FSH levels in the normal to abnormal range. However, they tend to respond and have chances for pregnancy as predicted by their highest FSH level.
Waiting for a menstrual cycle with a lower FSH level and then stimulating right away for IVF is not of any proven benefit.
Young women (under 35) with elevated FSH levels tend to stimulate better and have a much higher IVF success potential than “older” women. The better egg quality in the younger women can compensate for the quantity problem.
Day 3 estradiol testing
A blood estradiol level on day 3 (we do it on any day between days 2 and 4) of the menstrual cycle is a way to potentially discover some of those women with a normal day 3 FSH that may in fact have decreased egg quantity and quality.
What we want on day three is a low FSH level in conjunction with a low estradiol level. If the FSH is normal but the estradiol level is elevated, the elevated estradiol will often be artificially “suppressing” the FSH level down to the normal range.
The idea of using day 3 estradiol levels as an adjunct in evaluating egg quantity and quality is relatively recent. Clearly defined cutoff values for normal are not well established. We like to see the day 3 estradiol less than about 80. We repeat borderline or abnormal results in another menstrual cycle to try to get a “true” FSH.
There is some evidence that an elevated day 3 estradiol indicates a problem with ovarian reserve. This is sometimes the case, but often the issue is just that the elevated estrogen level is “masking” the potential for detecting low reserve by suppressing FSH into the normal range.