What Is a FSH Test?

A follicle stimulating hormone (FSH) test is a blood test that is used to determine the amount of FSH in the blood. This hormone is produced by the pituitary gland in both humans and animals, and it regulates all of the reproductive processes. A doctor might have several reasons for ordering a FSH test, but it usually is done to assist in the diagnosis of problems related to fertility, menstruation and sexual development. This test, which might be requested for either adults or children, is performed by a laboratory technologist who draws blood into a vial from a vein, usually on the inside of an elbow. The blood is then sent to a laboratory where a medical technologist will do the FSH test to determine whether the level of follicle stimulating hormone in the sample is low or high, relative to what is the normal range for FSH.

Depending on age and gender, an FSH test showing that the hormone is either high or low has a different meaning. In women, the FSH test is often done to investigate infertility issues, to evaluate menstrual problems or to determine whether menopause has begun. An FSH test with below normal values in a female might indicate that she is infertile because she is not producing eggs, has polycystic ovary disease or has ovarian cysts, among other possibilities. Low values might also indicate a problem in the functioning of the pituitary gland. On the other hand, high levels of FSH in a woman will tell a doctor that her ovaries have stopped working and she has begun menopause.

In adult men, the FSH test is also used to diagnose infertility or other problems with the reproductive system. The follicle stimulating hormone signals the production of sperm, but when it is too high, it indicates that the testicles are not functioning properly. Low levels of FSH in men might be associated with problems either in the pituitary gland or the hypothalamus.

For children, FSH tests might be requested if a girl or boy seems to be entering puberty either too early or too late. High levels of FSH in children might indicate premature puberty and need to be investigated to determine the underlying cause. If puberty seems to be delayed, normal to low levels of FSH can also be a symptom of other underlying problems.