Follicle-Stimulating Hormone (FSH) – Function & Levels
Follicle-stimulating hormone (FSH) is a key hormone produced by the pituitary gland that regulates the maturation of eggs and sperm, playing a central role in human fertility.
Things worth knowing about "Follicle-stimulating hormone"
Follicle-stimulating hormone (FSH) is a key hormone produced by the pituitary gland that regulates the maturation of eggs and sperm, playing a central role in human fertility.
What is Follicle-Stimulating Hormone (FSH)?
Follicle-stimulating hormone (abbreviated FSH), also known as follitropin, is a gonadotropin – a hormone that stimulates the gonads (ovaries and testes). It is produced and released by the pituitary gland, a small gland located at the base of the brain. FSH is essential for reproductive function in both women and men.
Biological Functions
FSH in Women
In women, FSH promotes the growth and maturation of ovarian follicles – small, fluid-filled sacs in the ovaries that each contain an immature egg cell. Under FSH stimulation, one or more follicles develop until one reaches full maturity, ultimately releasing the egg during ovulation. FSH also stimulates the ovaries to produce oestrogen.
FSH in Men
In men, FSH acts on the Sertoli cells of the testes, which support and nourish developing sperm cells. This makes FSH essential for spermatogenesis (sperm production) and male fertility.
Regulation of FSH Levels
FSH production is tightly regulated by a hormonal feedback loop:
- The hypothalamus releases gonadotropin-releasing hormone (GnRH), which stimulates the pituitary gland to secrete FSH.
- Sex hormones produced by the gonads (oestrogen, testosterone) and the protein hormone inhibin suppress FSH release through negative feedback.
- In women, FSH levels fluctuate throughout the menstrual cycle: they rise at the beginning of the cycle, trigger ovulation mid-cycle (pre-ovulatory peak), and decline during the luteal phase.
Normal FSH Levels
Reference ranges for FSH in the blood vary by sex, age, and menstrual cycle phase:
- Women (follicular phase): approx. 3–10 IU/L
- Women (ovulation): approx. 4–25 IU/L
- Women (luteal phase): approx. 2–8 IU/L
- Women (menopause): > 25–40 IU/L
- Men: approx. 1–12 IU/L
Exact reference ranges may differ between laboratories. Results should always be interpreted by a qualified healthcare professional.
Diagnosis: When is FSH Measured?
FSH blood levels are commonly measured as part of hormonal testing. Typical indications include:
- Evaluation of infertility in women and men
- Investigation of irregular or absent menstrual periods
- Suspected premature menopause (premature ovarian insufficiency)
- Assessment of delayed or early puberty
- Evaluation of pituitary gland function
- Monitoring during assisted reproduction (e.g., IVF treatments)
Causes and Significance of Abnormal FSH Levels
Elevated FSH Levels
High FSH levels may indicate the following conditions:
- Menopause or perimenopause in women
- Premature ovarian insufficiency (POI) – early loss of ovarian function
- Klinefelter syndrome in men (a chromosomal condition associated with reduced testicular function)
- Primary hypogonadism – inadequate function of the gonads
- Certain chromosomal or genetic disorders
Low FSH Levels
Low FSH levels may be associated with:
- Hypopituitarism (insufficient function of the pituitary gland)
- Hypothalamic amenorrhoea (e.g., caused by excessive exercise, low body weight, or severe stress)
- Secondary hypogonadism
- Use of certain medications (e.g., anabolic steroids)
FSH as a Medical Treatment
Synthetic or urine-derived FSH is used as a medication in assisted reproductive technology (ART), such as in vitro fertilisation (IVF). The goal is to stimulate the controlled growth of multiple follicles simultaneously, increasing the number of eggs available for retrieval. FSH-based therapies are also used in certain cases of male infertility to support sperm production.
References
- Anawalt BD et al.: Follicle-stimulating hormone and male fertility. In: UpToDate, Wolters Kluwer, 2023.
- World Health Organization (WHO): Laboratory Manual for the Examination and Processing of Human Semen, 6th Edition. WHO Press, Geneva, 2021.
- Boron WF, Boulpaep EL: Medical Physiology, 3rd Edition. Elsevier, Philadelphia, 2017.
Most purchased products
For your iron balance
Specially formulated for your iron balance with plant-based curry leaf iron, Lactoferrin CLN®, and natural Vitamin C from rose hips.
For your universal protection
As one of the most valuable proteins in the body, lactoferrin is a natural component of the immune system.
For Healthy Oral Flora & Dental Care
Formulated lozenges with Dentalac®, lactic acid bacteria, and Lactoferrin CLN®The latest entries
3 Posts in this encyclopedia categoryBile flow optimization
Calcium phosphate absorption
Abscess capsule
Most read entries
3 Posts in this encyclopedia categoryMagnesiumcarbonat
Calorie content
Cologne list
Related search terms: Follicle-stimulating hormone