What is Follicle-Stimulating Hormone?

Longevity Testing
Written By NOVI Team

Key Takeaways

  • Follicle-stimulating hormone (FSH) is a key hormone of the reproductive system in both men and women.

  • FSH triggers the development of mature eggs or sperm in the ovaries or testes.

  • In women, FSH levels change through the menstrual cycle, fluctuate during the transition into menopause, and rise after menopause.

  • Low FSH levels can impact fertility in both men and women.

  • A variety of medical conditions and lifestyle factors can cause FSH levels to be either low or high.

  • The only way to know your FSH levels is through a blood test.

  • It’s important to interpret your FSH levels in the context of your levels of other hormones. Your doctor can help you to interpret your test results.

Follicle-stimulating hormone (FSH) is a key hormone of the reproductive system in both men and women. FSH is produced in the pituitary gland, which is located in the brain, and affects cells in the ovaries or testes. Changes in the level of this hormone can have significant effects on fertility, and can also reveal important information about the aging process. 

Functions of FSH in the Body

The main functions of FSH are related to fertility and reproduction. The levels of FSH are normally low in children, and then rise as a person approaches puberty. FSH plays a major role in the development of eggs and sperm.

In Women

In a woman’s ovaries, eggs are contained in small sacs known as follicles. Each month, in the early part of the menstrual cycle, the pituitary gland begins to secrete FSH. This hormone triggers some of the follicles in each ovary to begin maturing. Usually, one follicle will become fully mature before the others do. The mature follicle begins to secrete estrogen, which suppresses the release of FSH and stops additional follicles from maturing.

The egg from the mature follicle is released in the middle of the menstrual cycle, in the process known as ovulation. Without healthy levels of FSH, follicles will not mature, and ovulation will not occur, leading to infertility.

In Men

FSH is also an important reproductive hormone in the male body. In men, levels of this hormone stay relatively constant after puberty, rather than cycling monthly as they do in women.

FSH acts on cells in the testes to promote the development and maturation of sperm. Healthy FSH levels support a healthy sperm count, while unhealthy levels may lead to infertility in men.

Follicle-Stimulating Hormone and Menopause

In Singapore, the average age of menopause is 49. As women approach the transition into menopause, they experience shifts in the levels of many hormones, including FSH. 

Changes in FSH Levels During Menopause

As a woman approaches menopause, her ovaries release much lower levels of estrogen. Normally, estrogen suppresses the release of FSH. As estrogen levels drop, FSH levels begin to rise. 

Perimenopause is the transition period into menopause. This usually begins in a woman’s early to mid 40s and lasts for several years. During perimenopause, estrogen levels fluctuate, and FSH levels will fluctuate along with them. When estrogen levels spike, FSH levels will drop. When estrogen levels drop, FSH levels rise.

After a woman has completed the transition into menopause, her estrogen levels stay persistently low. Because of this drop in estrogen, her FSH levels rise very high, and they will generally stay that way for the rest of her life.

FSH as a Marker for Menopause

A blood test for FSH is often used as a way to check whether a woman has gone through menopause. If FSH levels are high, this is an indicator that her ovaries are making less estrogen, which probably indicates that menopause has occurred.

However, estrogen levels can fluctuate a lot during perimenopause, and FSH levels will fluctuate along with them. Because of this, a single blood test for FSH isn’t enough to say for sure that a woman has gone through menopause. Her estrogen levels could still be fluctuating, and she still might be ovulating, at least occasionally.

If two separate tests, taken at least 4 to 6 weeks apart, both show high FSH levels, then it’s much more likely that a woman has finished menopause. Still, FSH is usually not used as the sole indicator of menopause. An FSH test is used along with symptoms, such as whether a woman is still menstruating and whether she’s experiencing symptoms like hot flushes and night sweats.

FSH testing may be used in a woman who is experiencing infertility, to assess where she’s at in the reproductive aging process. Increases in FSH levels are one of the earliest signs that the ovaries are shutting down their production of eggs. If a woman’s ovaries stop functioning before the age of 40, this is known as primary ovarian insufficiency. If this happens between the ages of 40 and 44, it’s known as early menopause. Persistently high FSH levels, along with other types of testing, may be helpful in determining which infertility treatments are most likely to be effective.

Testing for FSH Levels

The only way to know your FSH levels is to have a blood test. This test must be ordered by a qualified physician, and may be performed for a variety of reasons, including: 

  • Infertility

  • Menstrual cycle irregularities

  • Signs of possible polycystic ovary syndrome (PCOS)

  • Low sperm count

  • Signs of a possible pituitary disorder

  • Assessing where a woman is in the menopausal transition

The timing of the test is very important. Because FSH levels normally vary during the menstrual cycle, the results can be significantly affected by which day of the menstrual cycle the blood sample is taken. In general, FSH testing is performed on day 3 of the menstrual cycle. (Day 1 is defined as the first day of menstrual bleeding.)

FSH testing is usually performed along with tests of other hormones, such as luteinizing hormone (LH), another hormone involved in fertility and reproduction. Levels of testosterone, estrogen, and progesterone are often tested as well. By comparing the levels of these different hormones with each other, your doctor can get a complete picture of the overall function of your reproductive system. 

Understanding Your FSH Levels

If you have an FSH test, your doctor will interpret your test results and help you understand your levels. We can provide some general guidelines here, but it’s important to consider your results in the context of your symptoms and medical history as well as your levels of other hormones. This is why it’s so important to talk with a doctor to understand your results and to make a plan for addressing any abnormalities.

Normal FSH Levels

FSH levels vary by age and gender. For premenopausal women, they vary according to the phase of the menstrual cycle as well. According to the US Centers for Disease Control and Prevention, the normal ranges for FSH are: 

  • Men: 1.5 to 12.4 mIU/mL

  • Premenopausal women in the follicular phase (first half of the menstrual cycle): 3.5 to 12.5 mIU/mL

  • Premenopausal women at ovulation: 4.7 to 21.5 mIU/mL

  • Premenopausal women in the luteal phase (second half of the menstrual cycle): 1.7 to 7.7 mIU/mL

  • Postmenopausal women: 25.8 to 134.8 mIU/mL

A woman’s odds of getting pregnant are best if her day 3 FSH level is below 10 mIU/mL. This indicates that her ovaries are still likely to be producing mature follicles each month.

High FSH Levels

There are a few common causes of high FSH levels: 

  • Menopause

  • Aging in men

  • Primary ovarian insufficiency (a condition in which the ovaries stop functioning normally) 

  • Polycystic ovary syndrome (PCOS)

  • Damage to the ovaries or testes from an injury, a tumor, or cancer treatment (chemotherapy or radiation therapy)

  • Conditions affecting the adrenal glands, kidneys, or liver

  • Lifestyle factors, such as high stress levels or excessive alcohol intake

  • Genetic conditions

Low FSH Levels

Low FSH levels may be caused by: 

  • Polycystic ovary syndrome (PCOS)

  • Obesity

  • Conditions of the pituitary gland or hypothalamus (the part of the brain that controls the pituitary gland)

  • Certain medications, including oral contraceptives and steroids as well as certain psychiatric medications

  • Being very underweight or losing a lot of weight very quickly, or exercising excessively

  • Lifestyle factors, such as high stress levels or excessive alcohol intake

  • Chronic medical conditions, such as thyroid disease or diabetes

  • Genetic conditions

Note that some conditions can lead to either low or high FSH levels. This is why it’s important to interpret your FSH levels in context.

Symptoms of Imbalanced FSH Levels

The symptoms of either low or high FSH levels are similar, and include:

  • Infertility

  • Absent or irregular menstrual cycles

  • Low sperm count

Managing Abnormal FSH Levels

If your FSH levels are high or low, there are a few ways to manage this. 

  • Addressing underlying causes. If your FSH levels are being affected by an underlying medical condition, then treatment for this condition will help to bring your FSH levels back into the normal range. If you’re taking a medication that affects your FSH levels, switching medications may be an option to help normalize your hormone balance.

  • Lifestyle changes. If your stress levels are high, then managing your stress will help to normalize your hormone levels. If you drink alcohol, moderating your intake or quitting drinking altogether will be helpful. 

  • Weight management. If your body weight is too low, gaining a small amount of weight can make a significant difference for your hormone balance. If your body weight is too high, then weight loss will help. This may be accomplished through lifestyle changes alone or with the help of weight loss medications known as GLP-1 RAs.

  • Fertility treatments. If you’re currently trying to conceive and your FSH levels are low, then injections of FSH may be an option to help your body produce more mature eggs or sperm. If your FSH levels are high, then you may want to consider egg and/or sperm donation.

  • Hormone replacement therapy. If you have high FSH levels due to being in perimenopause or menopause, hormone replacement therapy (HRT) may be an option to help you manage any symptoms you’re experiencing. There are both benefits and risks to HRT, so it’s important to have a thorough discussion with your doctor before making a decision.

Healthy FSH Levels and Well-Being

FSH is a critical hormone for fertility and reproductive health. Your FSH levels can be impacted by aging and menopause, as well as by a variety of different medical conditions and lifestyle factors. Knowing your levels can help you to make a plan to optimize your fertility, and can also be useful in optimizing your overall health and longevity.

Hormone balance is complex, and it’s crucial to consider your FSH levels in context. Make sure to tell your doctor about any symptoms you may be experiencing or concerns that you may have. This will help them to correctly interpret the results of your FSH test.

A comprehensive health screening, which includes measuring FSH levels along with other hormones as well as many other biomarkers, will give you a fuller picture of your current health risks and opportunities for optimization. NOVI Assessment Max goes beyond the standard diagnostics, offering a deep, data-driven evaluation of over 100 biomarkers to assess early cardiac, metabolic, hormonal, and age-related health risks.

With doctor-led guidance before and after testing, NOVI Assessment Max gives you clear, personalized insights and an actionable health plan. This allows you to have a better understanding of your health so you can take the right steps toward better long-term health.

NOVI Team
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