Follicle-Stimulating Hormone (FSH) Test

Test Overview

A follicle-stimulating hormone test measures the amount of follicle-stimulating hormone (FSH) in a blood sample. FSH is produced by the pituitary gland.

FSH helps control the menstrual cycle and the production of eggs by the ovaries. FSH also helps control the production of sperm.

The amount of FSH varies throughout the menstrual cycle. It's highest just before the release of an egg (ovulation). The amount of FSH that controls sperm production normally stays at a constant level.

The FSH level can help find out if sex organs (testicles or ovaries) are working as they should.

Why It Is Done

The amount of FSH is measured to:

• Help find the cause of infertility.
• Help diagnose menstrual problems.
• See why a child is going through early or delayed puberty.
• Help diagnose certain pituitary gland problems, such as a tumor.

How To Prepare

Many medicines, such as cimetidine, clomiphene, digitalis, and levodopa, can change your test results. You may be asked to stop taking medicines (including birth control pills) that contain estrogen or progesterone or both for up to 4 weeks before you have a follicle-stimulating hormone (FSH) test. Make sure your doctor has a complete list of all the prescription and over-the-counter medicines you take, including herbs and natural substances.

How It Is Done

A health professional uses a needle to take a blood sample, usually from an arm. Sometimes more than one blood sample may be needed. A sample may be taken each day for several days in a row.

How long the test takes

The test will take a few minutes.

Watch

How It Feels

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.

Risks

There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Results

Normal

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

Many conditions can change FSH levels. Your doctor will discuss any significant abnormal results with you in relation to your symptoms and past health.

High values

High FSH values may mean:

• A genetic disease is present, such as Klinefelter syndrome.
• Loss of ovarian function before age 40 (premature ovarian failure).
• Low egg supply (ovarian reserve).
• Testicles are absent or not working as they should.
• Testicles have been damaged by a disease or by treatments, such as X-rays or chemotherapy.

High values in children may mean that puberty is about to start.

Low values

Low FSH values may mean:

• The sex organs (testicles or ovaries) are not working as they should.
• An area of the brain (the hypothalamus or pituitary gland) is not working as it should.
• A tumor is present that interferes with the brain's ability to control FSH production.
• Stress.
• Starvation or being very underweight.