Guide to Follicle-Stimulating Hormone (FSH)

WRITTEN BY

The Levels Team

Updated: 05/22/2025|12 min read

Summary

Follicle-stimulating hormone (FSH) plays a role in sexual development and reproductive health in both females and males. Testing FSH levels helps evaluate fertility issues, determine ovarian and testicular function, and diagnose hormonal disorders affecting reproductive health.

Why It Matters

FSH is made in your pituitary gland, a gland at the base of your brain that controls many hormones.

In women, FSH stimulates the growth of ovarian follicles and stimulates eggs to grow and prepare for ovulation. It's naturally higher right before ovulation. The pituitary gland releases FSH in response to signals from the hypothalamus (another part of the brain), and FSH levels fluctuate throughout the menstrual cycle, peaking just before ovulation. For men, FSH is involved in sperm production. It stimulates cells in the testes called Sertoli cells, which nurture and support developing sperm cells. Without adequate FSH, sperm count and quality can diminish, potentially affecting fertility.

The test is helpful in identifying possible causes of infertility. It also helps diagnose other reproductive issues, like missed periods and menopause in females, along with other underlying conditions.

High levels of FSH may be a sign that the ovaries or testicles are not making normal levels of sex hormones, like estrogen and testosterone. Estrogen in women and testosterone in men send signals to the brain to inhibit FSH production, so inadequate levels of these sex hormones can let FSH production go unchecked.

In women, high FSH levels may be due to conditions like primary ovarian insufficiency (POI), or menopause. In men, it could be a sign of primary testicular failure or injury to the testicles.

Associated Symptoms 

FSH levels themselves are laboratory findings rather than medical conditions. However, abnormal levels may be associated with various health issues, each with its own symptoms.

Common symptoms that may indicate conditions associated with high FSH levels:

• Irregular or absent menstrual periods: Can indicated diminished ovarian function or approaching menopause
• Hot flashes and night sweats: May be a result from hormonal fluctuations common during perimenopause or menopause
• Decreased libido: May occur due to hormonal imbalances affecting sexual desire
• Difficulty conceiving: Elevated FSH can indicate reduced ovarian or testicular function, affecting fertility
• Reduced sperm count (in men): Can result from testicular dysfunction despite the body's attempts to stimulate sperm production with high FSH

Common symptoms that may indicate conditions associated with low FSH levels:

• Delayed puberty: Insufficient FSH can prevent normal sexual development and maturation
• Infertility: Inadequate FSH may prevent proper egg maturation or sperm production
• Irregular or no menstrual periods: Can result from insufficient hormonal stimulation of the ovaries
• Poor sperm production (in men): May lead to reduced fertility due to inadequate stimulation of the testes

It's important to note that many people with abnormal FSH levels may experience no symptoms at all, especially with mild imbalances. The pattern, severity, and progression of symptoms, combined with laboratory findings, help healthcare providers determine the underlying cause.

Clinical Ranges

Female:

• Follicular Phase: 2.5-10.2 mIU/mL
• Mid-Cycle Peak: 3.1-17.7 mIU/mL
• Luteal Phase: 1.5-9.1 mIU/mL
• Postmenopausal: 23.0-116.3 mIU/mL

Male:

• Lab Reference Range: 1.4-12.8 mIU/mL

Lifestyle Factors That Can Impact It

Activities that may have a positive impact on FSH levels include:

• Moderate exercise: Regular moderate exercise helps maintain healthy hormone levels.
• Diet and Nutrition: A balanced diet rich in essential nutrients supports proper hormone production.  

Activities that may have a negative impact on FSH levels include:

• Excessive exercise. Exercising too much can suppress FSH production, particularly in women. 
• Disordered eating. People with eating disorders may experience particularly low FSH levels. Severe caloric restriction or malnutrition can disrupt FSH secretion. 
• Stress: Chronic stress can affect the hypothalamic-pituitary axis, which affects FSH production.
• Poor sleep habits: Poor sleep can disrupt hormone production. 
• Endocrine disruptors: Environmental chemicals like certain pesticides, plastics, and industrial compounds can interfere with normal hormone signaling and affect FSH levels.

Other Factors That Can Impact It

Genetic Conditions

• Inherited disorders affecting pituitary function
• Turner syndrome, a chromosomal disorder that affects females
• Klinefelter syndrome, a chromosomal disorder that affects males

Medical Conditions

• Hypothalamic amenorrhea: A condition where hormone imbalances stop menstruation, often due to low body weight or excessive exercise.
• Head injury: Brain trauma can affect the hypothalamus and pituitary gland, potentially disrupting FSH production and release.
• Pituitary tumors: Both benign and malignant tumors can affect FSH production and release.
• Endometriosis: A condition where tissue that mimics the endometrium grows in other areas of the body, potentially affecting hormone levels and fertility. (In rare cases, the condition can also occur in men.)
• Menopause: Estrogen levels decline with age, ultimately leading to menopause, the absence of menstruation for a full year.
• Note that during perimenopause, FSH levels fluctuate wildly, so a single measurement should never be used to "diagnose" menopause.

Medications and Supplements

• Birth control pills
• Certain antidepressants
• GnRH agonists and antagonists

Individual Factors

• Age: FSH naturally increases with age in both men and women, with dramatic increases in women during menopause and gradual increases in men with aging.
• Sex: Women's FSH levels change throughout their menstrual cycle, while men maintain relatively stable levels, and reference ranges differ between sexes.
• Pregnancy: FSH levels drop significantly during pregnancy because high levels of estrogen and progesterone suppress its production.

Testing Accuracy and Stability

FSH tests are generally accurate, but certain factors may suppress or elevate levels.

Factors That Can Affect the Accuracy of Your Test 

• Day of menstrual cycle (in women)
• Certain medications, such as oral contraceptives, antipsychotics, and some antiseizure medications 
• Acute illness
• Recent hormone therapy

How It Relates to Other Markers

Your healthcare providers may order other tests to look at factors that may be contributing to the abnormal FSH levels. Some other tests they might look at include:

• Luteinizing Hormone (LH): Works closely with FSH in reproductive function and helps distinguish between different types of hormone disorders.
• Estradiol: This is the primary female sex hormone, though it is also necessary for the male body. Levels of estradiol can shed light on ovarian and testicular function and pituitary health.
• Testosterone: A hormone found in both men and women. It is useful in assessing reproductive health and pituitary issues.
• Thyroid function tests: Thyroid disorders can affect reproductive hormone levels and are often evaluated alongside FSH.
• Anti Mullerian Hormone: This marker helps assess ovarian reserve and is often measured alongside FSH to evaluate fertility potential and reproductive aging.

What Results May Mean in the Context of Other Markers

• High FSH + High LH: May be related to primary gonadal failure (ovaries or testes not functioning properly) or menopause
• Normal FSH + High LH: May indicate PCOS in women
• Low FSH + Low LH: Can be an issue with pituitary or hypothalamic function, or presence of oral contraceptives or other medications
• High FSH + Low Estradiol: Could be an indication of ovarian failure or of menopause
• High FSH + Low Testosterone: May reflect primary testicular failure

Follow-up Considerations

If your FSH levels are low or high, your provider may make some of the following recommendations. You should always speak to your doctor if you have medical questions or before making medical decisions.

When Re-Testing May Be Appropriate

• After significant lifestyle changes
• Following medication adjustments
• During different phases of menstrual cycle
• When monitoring treatment effectiveness
• During fertility treatment

Additional Testing Your Doctor May Consider

• Bone density scan for those with chronically high FSH
• Pituitary imaging if hormone regulation problems are suspected
• Genetic testing if inherited conditions are suspected

When Additional Care May Be Warranted

• Persistent irregular menstrual cycles
• Infertility 
• Signs of early puberty or delayed sexual development
• Severe menopausal symptoms
• Unexplained sexual dysfunction

Bibliography