FSH – Follicle-Stimulating Hormone Explained
FSH (follicle-stimulating hormone) is a hormone produced by the pituitary gland that regulates the development of eggs and sperm, playing a key role in human reproduction.
Things worth knowing about "FSH"
FSH (follicle-stimulating hormone) is a hormone produced by the pituitary gland that regulates the development of eggs and sperm, playing a key role in human reproduction.
What is FSH?
FSH stands for follicle-stimulating hormone, a glycoprotein hormone belonging to the group of gonadotropins. It is produced and secreted by the anterior pituitary gland and plays a fundamental role in regulating the reproductive systems of both women and men.
Functions of FSH
In Women
In women, FSH stimulates the growth and maturation of ovarian follicles – the fluid-filled sacs that contain eggs. It also promotes the production of estrogen by the follicular cells. FSH levels fluctuate throughout the menstrual cycle and peak just before ovulation.
In Men
In men, FSH is essential for sperm production (spermatogenesis) in the testes. It acts on Sertoli cells, which support and nourish developing sperm cells.
Regulation of FSH Release
FSH secretion is controlled by the hypothalamus via gonadotropin-releasing hormone (GnRH). A negative feedback loop involving sex hormones – estrogen, progesterone, and testosterone – ensures that FSH levels remain balanced in the body.
FSH Testing and Normal Values
FSH levels are measured through a simple blood test. Normal values vary depending on sex, age, and cycle phase:
- Women (follicular phase): approx. 3–10 IU/L
- Women around ovulation: approx. 4–25 IU/L
- Postmenopausal women: above 25 IU/L
- Men: approx. 1–12 IU/L
Reference ranges may vary slightly between laboratories.
Elevated FSH Levels
High FSH levels typically indicate reduced gonadal function, as the pituitary gland compensates by releasing more FSH. Common causes include:
- Menopause or perimenopause in women
- Premature ovarian insufficiency (primary ovarian insufficiency)
- Klinefelter syndrome in men
- Testicular damage from radiation or chemotherapy
- Turner syndrome
Low FSH Levels
Low FSH levels may point to impaired function of the pituitary gland or hypothalamus. Possible causes include:
- Hypopituitarism
- Hypothalamic amenorrhea
- Hyperprolactinemia
- Certain pituitary tumors
Clinical Relevance
FSH measurement is an important part of evaluating fertility disorders, menstrual irregularities, and menopausal symptoms. In children, abnormal FSH values may indicate precocious or delayed puberty. FSH also plays a central role in assisted reproductive technology such as in vitro fertilization (IVF), both as a diagnostic marker and as a therapeutic agent in the form of recombinant FSH injections used to stimulate ovarian follicle development.
References
- Melmed, S. et al.: Williams Textbook of Endocrinology, 14th Edition. Elsevier, Philadelphia 2019.
- European Society of Human Reproduction and Embryology (ESHRE): Guideline on the Management of Premature Ovarian Insufficiency. 2016. Available at: https://www.eshre.eu
- Bremner, W.J.: Contraception and Reproductive Medicine. National Institutes of Health, PubMed Central. Available at: https://www.ncbi.nlm.nih.gov/pmc
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