What Is FSH? Follicle Stimulating Hormone: Function, Normal Levels, Tests, and Symptoms

Follicle stimulating hormone, or FSH, is a crucial player in your body's endocrine system, acting as a master regulator for puberty, fertility, and overall reproductive health. Though often discussed in the context of female fertility, this hormone is vital for men and women alike, from fetal development through to old age.

Recognizing when to see a doctor to test FSH levels to know more about your hormonal health is crucial. Learning about conditions related to FSH levels can help you make informed decisions regarding fertility, menopause, or even puberty. So, what is the FSH hormone?

What Is Follicle Stimulating Hormone?

Follicle stimulating hormone, FSH, is a critical hormone involved in human reproductive health. It is a type of gonadotropin, a hormone that acts on the gonads (the ovaries in women and the testes in men).

FSH’s meaning stems from its primary role in females, which is stimulating the growth of ovarian follicles in the ovary before egg release during ovulation. In males, FSH plays a crucial role in stimulating spermatogenesis, the process by which sperm are produced. Consider it the "go" signal that triggers the reproductive organs to initiate their key functions.

Where Is Follicle Stimulating Hormone Produced?

It is produced and released by the anterior pituitary gland, a small, pea-sized gland at the base of your brain. However, the pituitary gland doesn't decide to release FSH on its own. It takes orders from the hypothalamus, a region of the brain located just above it.

Its release is triggered by gonadotropin-releasing hormone (GnRH) from the hypothalamus, forming part of the hypothalamic–pituitary–gonadal (HPG) axis, a complex feedback system that regulates reproduction. So, FSH's full form doesn't work alone; it operates in close partnership with another gonadotropin, called Luteinizing Hormone (LH), to regulate the reproductive system.

Other hormones finely tune FSH production:

• Inhibin (suppresses FSH)

• Estrogen and progesterone (regulate FSH levels in women)

• Testosterone (regulates FSH in men)

It is crucial to understand how the FSH hormone works and how abnormal levels may indicate health concerns such as infertility, hormonal imbalances, puberty, or menopause. 

FSH Hormone Function Across Life Stages

What does FSH do? FSH plays a vital role in sexual development in children and fertility in adults. The role of FSH changes significantly throughout a person's life, influencing development from before birth into the senior years.

Fetal development

Even in the womb, FSH plays a subtle role. It's involved in the early maturation of the ovarian follicles in female fetuses and the seminiferous tubules (where sperm will eventually be produced) in male fetuses.

Childhood and puberty

Hormone FSH levels remain low throughout childhood. As puberty approaches, the brain "wakes up" the HPG axis, and FSH levels begin to rise. This increase is a critical trigger for FSH in puberty, stimulating the ovaries to produce estrogen in girls and the testes to produce testosterone in boys, leading to the development of secondary sexual characteristics.

Adults

In adult women, FSH is a key driver of the menstrual cycle and ovulation. In adult men, it maintains consistent sperm production. Its function is central to fertility for both sexes during the reproductive years.

Menopause and aging

In women, as the ovaries age and the supply of eggs (ovarian reserve) diminishes, they become less responsive to FSH. To compensate, the pituitary gland produces much higher levels of FSH in an attempt to stimulate the ovaries. This sustained rise in FSH levels is a classic biological marker of perimenopause.

Role of FSH in the Menstrual Cycle

FSH is crucial during the first half of the menstrual cycle (follicular phase), when it stimulates follicular growth and estrogen production. As estrogen levels rise, they signal the pituitary to reduce FSH levels and trigger a surge in LH (and a smaller FSH spike), leading to ovulation. Its levels fluctuate predictably to orchestrate ovulation:

• Follicular Phase (First half): The cycle begins with a rise in FSH. This stimulates the development and growth of a group of ovarian follicles. As these follicles mature, they produce estrogen.

• Ovulation (Mid-cycle): As estrogen levels rise, FSH is initially suppressed. However, once estrogen reaches a high peak, it triggers a dramatic surge in both LH and, to a lesser extent, FSH. This surge directly triggers ovulation, causing the most mature follicle to rupture and release an egg.

• Luteal Phase (Second half): After ovulation, the remnant of the follicle (the corpus luteum) produces progesterone. Progesterone and inhibin B exert negative feedback on the pituitary gland, decreasing FSH levels and preventing the development of new follicles. If pregnancy doesn't occur, the corpus luteum breaks down, progesterone levels fall, and FSH begins to rise again, recruiting follicles for a new cycle. 

Because these hormonal fluctuations are key to identifying your fertile window, tracking them can be a highly empowering experience. Tools like the Hormone Monitor, App, and Wands provide a clearer view of your cycle than one-time lab tests. Tracking hormones helps identify if fluctuations are natural or due to other factors.

FSH and Pregnancy

For those trying to conceive, FSH is a crucial component of the fertility puzzle. It's not directly involved in maintaining pregnancy, but it's essential for making conception possible in the first place. What does FSH do for fertility? 

It stimulates the ovarian follicles to mature a healthy egg. Without enough FSH to kickstart this process, ovulation can't happen, making pregnancy impossible. Insufficient FSH significantly reduces the chances of conception.

Fertility specialists often measure FSH levels on day 3 of the menstrual cycle. This baseline level provides a snapshot of ovarian reserve (the quantity of remaining eggs). Higher-than-normal FSH levels at this stage may indicate reduced ovarian reserve, which can reduce the likelihood of pregnancy.

When you're focusing on fertility and egg health, it's wise to consider supportive measures as well. Taking a high-quality prenatal vitamin can help ensure your body has the nutrients needed for healthy egg development and early pregnancy. For those with abnormal FSH levels or other fertility concerns, consulting a fertility expert can be useful for personalized guidance and a clear path forward.

Urine FSH Test and FSH Blood Test

An FSH test measures the amount of follicle stimulating hormone in your blood or urine. It's a simple yet powerful diagnostic tool used to investigate a wide range of issues, from infertility to puberty disorders. 

FSH Test in Women

Fertility assessments usually involve testing on day 2 or 3 of the cycle to determine the baseline FSH level. A doctor may order an FSH test for a woman to:

• Investigate infertility or difficulty conceiving

• Determine the cause of irregular or absent menstrual periods

• Assess ovarian reserve

• Confirm the onset of perimenopause or menopause

• Diagnose a pituitary gland or hypothalamic disorder

For those seeking a more comprehensive look at their reproductive health, advanced options are available. The Panorama Lab Test provides a comprehensive panel that measures not only FSH but also AMH, TSH, fT4, free testosterone, and prolactin, offering a 360-degree view of your hormonal landscape.

FSH Test in Men

Men may undergo FSH testing when doctors suspect specific fertility issues, such as:

• Investigating infertility, especially when a semen analysis shows a low sperm count

• Evaluating conditions like erectile dysfunction or low libido

• Diagnosing disorders of the testes, pituitary gland, or hypothalamus

FSH Test in Children/Teens

In children, an FSH test helps a doctor determine the cause of:

• Precocious (early) puberty: Signs of puberty appearing before age 8 in girls or 9 in boys

• Delayed puberty: Late signs of puberty in teenagers

Normal FSH Levels by Age Chart

Normal FSH ranges can vary based on your age, sex, and, for women, the phase of your menstrual cycle. It's crucial to remember that reference ranges may differ slightly between laboratories. Always discuss your results with your healthcare provider.

Low FSH: Causes and Implications

Low FSH levels (a condition called hypogonadotropic hypogonadism) indicate that the pituitary gland or hypothalamus is not functioning correctly. The gonads aren't receiving the signals they need to work.

Causes of Low FSH

• Pituitary or hypothalamic tumors or damage: Injury, radiation, or surgery affecting the brain.

• Kallmann syndrome: A rare genetic condition that causes delayed puberty and an impaired sense of smell.

• Lifestyle factors: Being severely underweight, engaging in excessive exercise, or experiencing extreme stress can suppress the HPG axis.

Symptoms of Low FSH

In women, this can lead to irregular or absent periods, infertility, and delayed puberty. In men, it can cause low sperm count, loss of sexual function, reduced muscle mass, and delayed puberty.

For those seeking to support their hormonal balance naturally, incorporating gentle lifestyle adjustments can be beneficial. Products like Mira Fertility Tea, with its blend of hormone-supportive herbs, can be a calming addition to your daily routine, promoting regular menstrual cycles and supporting overall well-being.

High FSH: Causes and Implications

High FSH levels, known as hypergonadotropic hypogonadism, show that the brain is trying to stimulate the gonads, but they are not responding. This condition is called primary ovarian or testicular failure. Causes of high FSH include genetic conditions, such as: 

• Klinefelter syndrome in men

• testicular damage from viral infections, such as mumps

• chemotherapy, radiation, or physical injury

• autoimmune diseases, which can result in elevated FSH levels

What causes high FSH in women?

High FSH Levels in Females

• Menopause/Perimenopause: This is the most common cause and a natural part of the aging process. As the ovarian reserve declines, the ovaries produce less estrogen and Inhibin B. The pituitary gland increases FSH production in an unsuccessful attempt to stimulate the less responsive ovaries. 

• Genetic Conditions: Turner syndrome in women, but Klinefelter syndrome in men.

• Primary Ovarian Insufficiency (POI): Defined as the loss of normal ovarian function before age 40. Ovaries fail prematurely, leading to a deficiency of estrogen and progesterone, which causes the pituitary gland to significantly increase FSH secretion. 

• Polycystic Ovary Syndrome (PCOS): High FSH is uncommon; usually, LH is elevated relative to FSH. FSH is typically normal or low because high estrogen and androgens suppress its release. Many women with PCOS benefit from supplements addressing insulin resistance and androgen excess, core aspects of the condition.

• Ovarian Tumors: In certain estrogen-producing tumors (like GCTs), the tumor itself overproduces estrogen. This high estrogen level provides strong negative feedback on the pituitary gland, suppressing FSH release and resulting in low FSH levels.

• Autoimmune Diseases: Autoimmune conditions that can be associated with POI and high FSH include autoimmune oophoritis, Addison's disease, autoimmune thyroid disease, and other forms of Polyglandular Autoimmune Syndrome (PAS) types 1-4.

Symptoms of Abnormal FSH Levels

The symptoms associated with either high or low levels of follicle stimulating hormone (FSH)  can vary significantly depending on an individual's age and sex. The presentation of symptoms can thus vary widely, underscoring the importance of considering factors such as age and biological sex when evaluating FSH-related health concerns.

In women:

• Irregular or absent menstrual periods (amenorrhea)

• Infertility caused by a lack of ovulation

• Delayed puberty in teenagers

• Hot flashes, vaginal dryness, and other menopausal symptoms (if estrogen is also low)

In men:

• Low sperm count and infertility

• Erectile dysfunction

• Decreased muscle mass and body hair

• Fatigue and low libido

• Delayed puberty in boys

In children:

• High FSH: Can indicate precocious puberty (breast development before age 8 in girls; testicular enlargement before age 9 in boys)

• Low FSH: May signify delayed puberty (no breast development by age 13 in girls; no testicular growth by age 14 in boys)

Conclusion

FSH, or follicle stimulating hormone, is crucial for regulating reproductive functions like fertility, puberty, and aging. Produced by the pituitary gland, it controls puberty, fertility, the menstrual cycle in women, and sperm production in men. Levels fluctuate with age and can signal health issues.

Testing FSH, along with other hormones, aids in evaluating fertility, irregular menstrual cycles, and menopause. If you have concerns about your hormones or fertility, it's essential to consult with a healthcare provider or a reproductive health specialist.

Frequently Asked Questions

What is the typical FSH level for a pre-menopausal woman?

For a pre-menopausal woman in the follicular phase (the first half) of her menstrual cycle, a typical FSH level is between 1.4 and 9.9 mIU/mL.

How to lower the FSH level?

FSH levels may be lowered by addressing underlying causes like stress, poor diet, or ovarian dysfunction; hormone therapy or fertility treatments may also help.

Why does FSH decrease after ovulation?

After ovulation, rising progesterone and estrogen provide negative feedback to the pituitary, reducing FSH production until the next cycle.

What is the need for doing the FSH test for people who are trying to get pregnant?

FSH testing helps assess ovarian reserve and determine if ovulation is occurring properly, both of which are crucial for natural conception and fertility treatments.

What does a positive FSH urine test mean?

A positive urine FSH test typically indicates elevated FSH levels, which can occur near ovulation or approaching menopause, depending on the person's age and unique situation.