Summary

• Follicle stimulating hormone (FSH) is one of the hormones that brings about sexual development in children. In adults, it regulates the menstrual cycle in females and triggers the making of sperm in males.
• Measuring the level of FSH in a sample of blood can help diagnose fertility and pituitary disorders.
• In children, it is used to investigate early or delayed puberty.
• The FSH test is typically requested together with other hormone tests such as luteinising hormone (LH), testosterone, oestradiol, and progesterone. 

What is follicle stimulating hormone (FSH)

Follicle stimulating hormone (FSH) is made in the pituitary gland and plays an important role in sexual development in children and fertility in adults.

In females, FSH is essential for the growth of eggs in the ovaries.

FSH works with another hormone, luteinising hormone (LH), to regulate the menstrual cycle (periods).

The level of FSH varies throughout the menstrual cycle and is highest just before ovulation. Ovulation is when an ovary releases an egg that can be fertilised by sperm. FSH stimulates the follicles in the ovaries, the small sacs of fluid that contain eggs, hence the name follicle stimulating hormone.

In males, FSH stimulates the growth of the testicles in puberty and tells the testicles to make sperm in adults.

In children, FSH and LH levels are normally low when the child is young but they rise closer to puberty. This begins the changes toward sexual maturity and development.

How is FSH made?

FSH is part of a complex feedback system of glands, hormones and sex organs that together regulate sexual development and function. As well as FSH, this involves LH and the reproductive hormones testosterone, oestradiol, and progesterone.

Hormones are chemical messengers that are made by your glands and travel in your bloodstream to control the actions of specific cells in your tissues or organs. When they reach their target, they attach to a cell’s receptors, stimulating a response.  

• The hypothalamus in the brain makes gonadotropin-releasing hormone (GnRH), which signals the pituitary gland to release FSH and LH into the bloodstream.
• FSH and LH trigger the ovaries (in females) or testicles (in males) to make the reproductive hormones oestradiol and progesterone (in females) and testosterone (in males).
• The amount of reproductive hormones made by the ovaries or testicles let your hypothalamus and pituitary gland know when to step up or slow the production of FSH and LH.

If any of the glands or organs in this system are not working as they should, abnormal levels of hormones are made.

Why get tested?

FSH testing is often used together with other tests including LH, testosterone, oestradiol and progesterone. Abnormal levels of FSH may be a sign of a problem in:

• the pituitary gland.
• the hypothalamus.
• reproductive glands – your ovaries or testicles.

These tests are used to investigate:

• infertility 
• low sperm count
• irregular periods 
• pituitary gland disorders
• menopause 
• delayed or early puberty

FSH, LH and ovarian hormones during the menstrual cycle

FSH testing is used along with other hormone tests to investigate irregular menstrual periods or confirm menopause. 

Day 0 is the first day of menstruation. FSH stimulates the growth of eggs in the ovaries during the first half of the menstrual cycle (follicular phase). It does this by causing the egg follicle to make oestradiol.

At about mid-cycle there is a surge of FSH and LH which is followed by ovulation - the release of the egg from a follicle at about day 14.  The fertile period begins about five days before the LH surge and ends the following day – the egg quickly degenerates if not fertilised.

During the second half of the menstrual cycle (luteal phase) FSH stimulates the production of progesterone.

Menstrual cycle times can vary widely between people. This makes it difficult to calculate the exact timing of the fertile period. As a woman ages and menopause approaches, ovarian function wanes and eventually stops and as this occurs, the levels of both FSH and LH rise.

Males

Normally, FSH levels do not change much throughout the course of a man’s life. The FSH test is used to find out if there is a problem with the testicles or what may be the cause of a low sperm count. It is also often used to investigate early or delayed puberty. LH is measured to investigate the cause of low testosterone levels.

Children

In children, FSH levels rise soon after birth and then fall to very low levels in infancy.  They remain low until puberty when levels begin to rise again. In girls, this stimulates the ovaries to make oestrogen. In boys, it stimulates the testicles to make testosterone.

Disorders affecting the hypothalamus, pituitary and/or the ovaries or testicles can cause too much or too little FSH to be made. This can result in conditions such as infertility, abnormal menstrual cycles, or early or delayed puberty.

Having the test

Sample

Blood

Any preparation?

None

Your results

Reading your test report
Your results will be presented along with those of your other tests on the same form.  You will see separate columns or lines for each of these tests.  

Results of an FSH test are typically considered with results of other hormone tests, such as LH, oestrogens, progesterone and testosterone.

Interpreting results

Female

• As part of an infertility investigation, a high or low FSH is not diagnostic but helps build a picture of what may be the cause of infertility. For example, a hormone imbalance may affect a woman’s menstrual cycle and/or ovulation. Your medical team will consider all test and clinical information to establish a diagnosis.
• FSH and LH levels can help differentiate between whether there is a problem with the ovaries or whether there is a disorder of either the pituitary gland or the hypothalamus.
  • Increased levels of FSH and LH are consistent with a problem with the ovaries.
  • Low levels of FSH and LH suggest a pituitary or hypothalamic problem.
• When a woman enters menopause, her ovaries stop working and FSH levels rise. In general, FSH rises more and earlier than LH. 

Males

• High FSH levels suggest a problem with the testicles. This can be due to developmental issues or an injury to the testicles.
• Low levels of FSH suggest pituitary or hypothalamic disorders.

Children

• A child experiencing early puberty will generally have higher levels of FSH and LH than expected for their age along with the development of secondary sexual characteristics such as pubic hair and breasts at an unusually young age. This is much more common in girls than in boys.
• For a child experiencing delayed puberty, LH and FSH levels can be normal or below what is expected for a person within their age range.

Reference intervals

Your results will be compared to reference intervals (sometimes called a normal range).

• Reference intervals are the range of results expected in healthy people. 
• When compared against them your results may be flagged high or low if they sit outside this range.
• Many reference intervals vary between labs so only those that are standardised or harmonised across most laboratories are given on this website.

If your results are flagged as high or low this does not necessarily mean that anything is wrong. It depends on your personal situation. Your results need to be interpreted by your doctor.

Any more to know?

• FSH levels can be higher with the use of some medications including cimetidine, clomiphene, and naloxone.
• FSH results can be falsely elevated in people who are taking large doses of biotin as this can interfere with the test method.
• FSH levels can be lower with oral contraceptives, phenothiazines and hormone treatments.
• For females, the test is usually done on the second or third day of the menstrual cycle, when FSH levels are at their highest.

Questions to ask your doctor

The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help. 

You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely. 

Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:

• Why does this test need to be done?
• Do I need to prepare (such as fast or avoid medications) for the sample collection?
• Will an abnormal result mean I need further tests?
• How could it change the course of my care?
• What will happen next, after the test?

More information

Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.

Get further trustworthy health information and advice from healthdirect.