How Follicle Stimulating Hormone (FSH) Helps Fertility Treatments

Follicle-stimulating hormone, or FSH, is a hormone released from the pituitary gland in the brain that stimulates an egg follicle to grow each month as part of the menstrual cycle.

An FSH test can be used to assess your ovarian reserve (the reproductive potential of your ovaries). Older people with ovaries tend to have elevated blood levels of FSH, which indicate ovarian maturing. This is because greater amounts of the hormone are required for the ovary to recruit and stimulate an egg follicle.

FSH Levels During Your Cycle

Throughout your menstrual cycle, levels of FSH vary. Healthcare provider s often test FSH levels on day 3 of your cycle. These are considered your baseline levels. FSH is part of a complex dance of hormones that includes luteinizing hormone (LH), estradiol, and gonadotropin-releasing hormone (GnRH).

GnRH is secreted from the hypothalamus and acts on the pituitary gland to release FSH. FSH stimulates an egg-containing follicle to grow. As the follicle grows, it releases estradiol, which triggers a surge of LH, prompting ovulation.

Normal baseline FSH levels are between 4.7 and 21.5 mIU/ml in women who are menstruating.

Certain medications, such as birth control pills, clomiphene, digitalis, and levodopa, can alter the test results. Your healthcare provider will instruct you to stop taking those drugs before taking an FSH test. In the case of hormonal birth control, it should be stopped at least a few weeks prior to taking the test.

FSH and Pregnancy Planning

People who do not ovulate regularly, have abnormal FSH levels, or are struggling to conceive should see a fertility specialist for help getting pregnant.

These specialists, known as reproductive endocrinologists, will first do some diagnostic testing and measure your FSH level as well as other hormones that impact your fertility. Then they can use a variety of medications and hormones to promote follicle development and ovulation to help you get pregnant.

Some people may be anxious to hear that shots or hormone injections are needed to stimulate the ovaries. While injections may be uncomfortable, it's important to keep your eyes on the bigger picture—having a baby.

FSH and Ovarian Reserve

FSH levels are used to test ovarian reserve (the number and quality of eggs a person has left). Your healthcare provider will have blood work drawn on the third day of your menstrual cycle. The results are typically available within 24 hours depending on the lab.

Based on the results of the lab tests, a fertility specialist can gauge how many eggs you have left and how likely you are to respond to fertility treatment.

At that point, menopause begins. FSH levels at menopause are consistently elevated to 30 mIU/mL and above.