FSH Blood Test - More Information

The FSH test, also known as the FSH blood test, follicle-stimulating hormone test and FSH lab test, measures the FSH blood level.

FSH is an important hormone in the fertility cycle (particularly in females). FSH is a special type of hormone known as a gonadotropin. It is produced in a gland in the brain known as the pituitary gland and plays an important role in various aspects of the growth and maintenance of the reproductive system. Typically, FSH, along with LH, is known for its function in female fertility and, in particular, ovulation. In line with its name, follicle-stimulating hormone stimulates the ovaries to grow follicles in the ovary for the process of ovulation. During the course of the menstrual cycle, one follicle in the ovary typically matures with the help of rising FSH levels and, with rising LH blood levels, causes release of the egg and both hormones. The mature follicle helps prevent additional follicles from being stimulated by releasing high levels of estradiol which gives feedback to the glands to shut down the production of FSH.

As part of a fertility workup, FSH levels are typically measured on the third day when it peaks. Abnormally high or low FSH levels can result in infertility in women. Given its close relationship with other hormones, FSH testing is often performed in conjunction with the estradiol test, LH test and progesterone test.

In addition to being high at specific times during the menstrual cycle, FSH levels can be elevated for other reasons. Most commonly, FSH blood hormone levels are elevated when a woman is in menopause. During menopause, the ovaries and other reproductive organs are unable to produce enough estradiol and other hormones to turn off FSH production by the glands. Not sensing any reason to shut off, the pituitary gland continues to produce high amounts of FSH. As a result, FSH is a hormone that is commonly measured as part of any menopause test panel. In women, FSH can also be abnormally elevated in situations when a woman's ovaries are not working properly (e.g. premature ovarian failure) - something that is often evaluated in conjunction with the AMH test for ovarian reserve. Other rarer conditions such as Klinefelter syndrome may also cause elevated FSH levels.

FSH does play a role in male fertility as well. By stimulating special cells in the testicles known as Sertoli cells, FSH helps the testicles produce sperm through a process known as spermatogenesis. In men, a low FSH level can affect sperm production.

FSH levels can be low for several reasons. One reason is that the gland that produces FSH - the pituitary - is malfunctioning and cannot produce follicle stimulating hormone. Abnormally low FSH production in this instance can, in some cases, be due to malformed cells or even cancer. Low FSH levels can also be found in people with high hormone levels such as testosterone or estrogens. High levels of these sex hormones exert negative feedback on the pituitary gland and tell it not to produce more follicle-stimulating hormone. Instances when this occurs include when someone is receiving hormone replacement therapy for testosterone or estrogen.

The FSH blood test is useful in making a diagnosis of premature ovarian failure. Premature ovarian failure (POF) is when the ovaries stop functioning before a woman reaches the age of 40, leading to infertility. In addition to high FSH levels, women with premature ovarian failure also tend to have very low estrogen levels. The diagnosis of premature ovarian failure is typically made by checking two follicle-stimulating hormone blood levels 30 days apart. In women with POF, the FSH levels will typically match the levels of a women who is post-menopausal (40mlU/mL).

Getting an FSH test at a lab near you is relatively straightforward. Since most lab locations have the standard equipment utilized to perform the FSH blood test, all you typically need to do is select the closest lab location. On the day of your appointment, a small amount blood will be drawn from your veins and the sample will be processed.

Some people wonder whether the FSH test is fasting or not. Because FSH levels are related to fertility cycles and not to diet, fasting is not necessary prior to getting this blood test. When should you take an FSH test? For women, in most cases, it is recommended that the FSH test is performed on day 3 of the cycle.

For a more detailed fertility lab test evaluation, check out the fertility test panel.