Evidence Based

FSH: Function, Tests, High & Low Levels + How to Normalize It

Written by Helen Quach, BS (Biochemistry) | Last updated:

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FSH and reproductive health

Follicle Stimulating Hormone (FSH) is a hormone that is vital for reproduction and puberty. Read more below to learn about its functions.

What is Follicle Stimulating Hormone?

Follicle Stimulating Hormone (FSH) is a gonadotropic hormone secreted by the pituitary gland. FSH is important for development during puberty and the function of reproductive organs [1].

Function In Men

In men, FSH acts on the testes to stimulate sperm production. FSH stimulates testicular growth and aids the production of an androgen-binding protein [1].

This androgen binding protein is crucial for the development of normal sperm production and for maintaining maturing sperm cells [1].

The production of FSH is regulated by the blood levels of testosterone and inhibin, both of which are produced in the testicles. If testosterone levels are high, FSH secretion decreases; if testosterone levels are low, FSH secretion increases [1].

Too Much FSH

Raised levels of FSH is a sign of malfunction in the testes. If the testes don’t produce enough testosterone, FSH production rises [2].

Too Little FSH

FSH is essential to normal sperm production. In the absence of FSH, puberty may not occur and infertility due to lack of sperm or low sperm quality may occur. Low FSH levels can cause delayed puberty and limited sperm production, but you can still be fertile [2].

Function In Women

In Women, FSH is essential to the pubertal development and the proper function of the ovaries. FSH regulates the secretion of estrogen [1].

When hormone levels fall towards the end of the menstrual cycle, the pituitary gland is stimulated to produce more FSH. This increase in FSH makes the ovary produce more estradiol and inhibin [1].

This increase in these two hormones, in turn, is sensed by the pituitary gland and less FSH will be released. FSH secretion rises in the first half of menstruation and decreases after ovulation. At the very end of the menstrual cycle, FSH starts to rise and the cycle begins again [1].

Too Much FSH

Just like with men, too much FSH is a sign that something is wrong. If the ovary fails to produce enough estrogen, FSH production rises. However, FSH levels rise naturally in women around the menopausal period [3].

Too Little FSH

A dearth of FSH can lead to a lack of development at puberty and ovarian malfunction. In women, FSH deficiency leads to infertility just like in men [4].

High FSH


In men, high FSH levels may indicate problems with the testes: when the testes don’t produce enough testosterone, FSH production rises [5].

In women, high FSH levels may indicate ovarian dysfunction or failure. If the ovaries do not produce enough estrogen, FSH production rises [6].

Menopausal women have naturally higher FSH levels [6].

The most common causes of high FSH levels include:

  • Menopause [6]
  • Gonadal dysgenesis (no functional ovaries) [7]
  • Autoimmune diseases, including thyroid disorders [8]
  • Klinefelter syndrome [9]
  • Turner’s syndrome [10]

Other causes of high FSH levels include:

  • Smoking [11]
  • Drugs, such as cimetidine (Tagamet) and spironolactone (Aldactone, Spiractin, Verospiron) [12, 13]
  • Viral infections, such as mumps [14]
  • Germ cell tumors [15]


  • Stomach pain [16]
  • Headache [17]
  • Abnormal menstrual cycles [18]
  • Decreased libido [19]
  • Infertility [20]


In postmenopausal women, chronically high FSH levels may increase the risk of osteoporosis, but decrease the risk of type 2 diabetes [21, 22].

How to Lower It


Eating a diet high in soy can help lower FSH levels. Large amounts of soy protein and isoflavones can suppress FSH levels [23].

Acupuncture may help lower FSH levels [24].


  • DHEA [25, 26]
  • Omega 3 fatty acids decrease FSH [27]
  • Traditional Chinese medicine, such as the Zishen Yutai pill  [28]



In men, low FSH can cause low sperm quality or infertility due to a lack of sperm production [5].

In women, low FSH can cause ovarian malfunction and infertility [29]. A lower FSH level is associated with a higher risk for ovarian cancer [30].

The most common cause of low FSH levels is improper pituitary gland function, which can be caused by:

  • Kallmann syndrome (an inherited disorder) [31]
  • Polycystic ovary syndrome (PCOS) [32]

Other causes of low FSH levels include:

  • Stress [33]
  • Hormonal drugs, such as estrogen, testosterone, steroids, and oral contraceptives [34, 35, 36, 37]
  • Anorexia [38]
  • An under-active thyroid gland (hypothyroidism) [39]
  • Hyperprolactinemia (a condition with high prolactin levels in the blood) [40]
  • Eating a diet with large amounts of soy protein and isoflavones [23]
  • Alcohol [41]
  • Meningitis [42]


  • Erectile dysfunction [40]
  • Irregular menstrual cycle [43]
  • Infertility (in the most severe cases) [6]


In postmenopausal women, low FSH levels are associated with a higher risk of diabetes and prediabetes [44].

How to Increase It


You should refrain from eating a diet with too much soy. Large amounts of soy protein and isoflavones can suppress FSH levels [23].

Reducing your alcohol intake may also prevent low FSH levels [41].


Follitropin Alfa

Follitropin alfa is a hormone identical to FSH. It is used as a fertility medicine to help develop eggs in the ovaries. It is also used as a fertility medicine to help men with low sperm counts produce more sperm [48].

Although it is generally safe, Follitropin alfa can cause headaches, nausea, and skin irritation [48].

FSH Testing

People normally measure their FSH levels when they are [6]:

  • Going through menopause
  • Having difficulty getting pregnant
  • Having irregular menstrual periods
  • Having symptoms of pituitary or hypothalamic disorders
  • Having symptoms of testicular or ovarian disease

An FSH test measures the amount of FSH in a blood sample. An FSH test is usually taken to determine why a couple can’t conceive a child [49].

A reading on FSH levels can reveal whether the ovaries or testes are functioning properly. An FSH test can be administered to check and evaluate for a low sperm count or egg supply [49].

This test can also be used to determine why a child is going through puberty early or late (or not at all). An FSH test can also help evaluate menstrual problems [49].

Normal Adult Reference Range:


  • Before puberty – 0 to 5.0 mIU/mL (0 to 5.0 IU/L)
  • During puberty – 0.3 to 10.0 mIU/mL (0.3 to 10.0 IU/L)
  • Adult – 1.5 to 12.4 mIU/mL (1.5 to 12.4 IU/L)


  • Before puberty – 0 to 4.0 mIU/mL (0 to 4.0 IU/L)
  • During puberty – 0.3 to 10.0 mIU/mL (0.3 to 10.0 IU/L)
  • Women who are still menstruating – 4.7 to 21.5 mIU/mL (4.5 to 21.5 IU/L)
  • After menopause – 25.8 to 134.8 mIU/mL (25.8 to 134.8 IU/L)

Irregular FSH Levels?

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About the Author

Helen Quach

BS (Biochemistry)

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