Follicle Stimulating Hormone, commonly known as FSH, is an important hormone in the reproductive processes of women. FSH levels affect the quality and quantity of her remaining eggs and can directly affect her chances of conceiving and sustaining a pregnancy.

As part of a basic fertility workup, your doctor will likely order blood work to check your FSH levels. This is a simple blood test meant to measure the amount of follicle-stimulating hormone (FSH) in your bloodstream during a certain point in your menstrual cycle, usually the 3rd day of your period.

FSH works closely with another hormone called luteinizing hormone to control sexual functions. So a luteinizing hormone test is often done along with an FSH test. These tests are most often used to:

• Help find the cause of infertility
• Find out if there is a problem with ovarian function.
• Find the reason for irregular or stopped menstrual periods.
• Confirm the start of menopause or perimenopause. Menopause is the time in a woman’s life when her menstrual periods have stopped and she can’t become pregnant anymore. It usually starts when a woman is around 50 years old.

FSH Levels

When trying to conceive, your Follicle Stimulating Hormone level needs to be below 15mIU/ml. When FSH levels are too high or too low, achieving pregnancy can become much more difficult because it affects your menstrual cycle and whether or not you ovulate.

High levels in women potentially could indicate:

• You’re not producing good quality eggs that are available for fertilization. This is a normal part of aging and is more common in women age 38 or older. However, even young women can have high FSH levels. For example, a woman in her 20s may have high FSH levels if she’s experiencing primary ovarian insufficiency (premature ovarian failure).

•Ovarian failure or loss of ovarian function.

•Chromosomal abnormality.

• Polycystic ovary syndrome (PCOS).

• Started menopause or are in perimenopause.

• An ovarian tumor.

•Turner syndrome, a genetic disorder that affects sexual development in females. It often causes infertility.

Low FSH Levels

• Your ovaries are not making enough eggs.

• Your pituitary gland is not working correctly.

• You have a problem with your hypothalamus, a part of the brain that controls the pituitary gland and other essential body functions.

•You are very underweight.

FSH levels and IVF treatment

FSH levels are also used to evaluate whether in vitro fertilization (IVF) treatment or injectable fertility drugs could be effective. Women with high FSH levels or poor ovarian reserves are less likely to respond to high doses of fertility drugs. Depending on how high FSH levels are, some doctors will discourage IVF treatment because the cycle is more likely to be canceled or fail.

When FSH levels are abnormally high, it’s because eggs are not maturing with normal levels of FSH. The body will try to fix the problem by increasing FSH. With IVF or injectable fertility drugs, the hormone FSH is being injected to stimulate your ovaries.

If your ovaries aren’t responding to your natural FSH, they are also unlikely to respond to injected FSH. In a woman with good ovarian reserves, injected FSH will lead to strong egg growth in her ovaries. In a woman with poor ovarian reserves, the ovaries will not respond as well.