Why men need it for fertility and testicular function
Follicle-stimulating hormone (FSH) belongs to the group of gonadotropins produced by the pituitary gland and is a key regulator of male fertility. Although its name is familiar from women's medicine, where it stimulates the growth of egg follicles, FSH also plays a crucial role in men: it stimulates sperm production in the testes and ensures the healthy function of the Sertoli cells , which are responsible for the development of mature sperm cells.
An imbalanced FSH level can indicate fertility problems, hormone deficiencies , or disorders of the hypothalamic-pituitary-testicular axis . FSH testing is essential for men with an unfulfilled desire to have children or an abnormal sperm analysis, as well as in the context of testosterone therapy or libido problems.
What is FSH and what does it do in the male body?
FSH is produced in the pituitary gland and, like luteinizing hormone (LH), is transported via the bloodstream to the testes. While LH stimulates testosterone production in the Leydig cells, FSH stimulates spermatogenesis in the Sertoli cells – that is, the formation and maturation of sperm cells.
Over and beyond:
- It activates the Sertoli cells in the testicles
- Promotes the maturation of immature sperm
- stabilizes the local testicular environment
- supports the effect of testosterone on sperm production
When should FSH be tested in men?
An FSH test is useful in the following cases:
- Unfulfilled desire to have children
- Low sperm count or poor sperm quality
- Erectile problems or loss of libido
- Suspected primary testicular failure
- Evaluation of hypogonadism (testosterone deficiency)
- Before or during testosterone therapy (TRT)
What does a low or high FSH level mean?
Elevated FSH:
An elevated FSH level can indicate primary testicular insufficiency – meaning the testicles no longer respond adequately to control signals from the brain. Possible causes:
- genetic syndromes (e.g. Klinefelter)
- testicular inflammation
- Zn Chemotherapy / Radiation therapy
- Alcohol or nicotine abuse
- aging processes
Low FSH:
Low levels can be a sign of a disorder in the pituitary gland or hypothalamus . Possible causes include:
- chronic stress (cortisol inhibits gonadotropin release)
- Medications such as opiates or anabolic steroids
- very low body fat percentage / excessive training
- Tumors or injuries in the brain
- secondary hypogonadism
If FSH is suppressed by external factors (e.g., by TRT), temporary infertility can occur – an aspect that should definitely be considered before undergoing TRT.
How is FSH measured?
FSH is measured in blood serum , ideally in the morning and on an empty stomach. It is important not to consider the value in isolation, but always in conjunction with:
- LH (Luteinizing Hormone)
- Total and free testosterone
- SHBG
- Prolactin
- Sperm analysis (for those wishing to conceive)
- If necessary, estradiol for extended fertility diagnostics
What are normal FSH levels?
Reference values for men vary slightly depending on the laboratory:
- Normal range : approx. 1.5 – 12 IU/l
- Values > 12 IU/l : Suspected testicular dysfunction
- Values < 1.5 IU/l : Indication of a central cause (pituitary or hypothalamic disorder)
An individual assessment is crucial - especially for men with symptoms but borderline values.
What can influence FSH levels?
- Stress increases cortisol, lowers FSH
- Alcohol and smoking impair testicular function
- Body fat percentage - severe obesity can lower FSH
- Age - FSH increases slightly with age
- Anabolic steroids suppress the body's own FSH production (regardless of whether it's medically supervised TRT or misuse).
- Medications and environmental toxins
How can an imbalanced FSH level be treated?
The therapy depends on the cause:
- In cases of primary testicular failure : No direct therapy is possible – sperm preservation may be an option.
- In cases of central hormonal suppression : stress reduction, dietary changes, micronutrients
- If TRT is planned : ensure fertility, if necessary TRT in combination with recombinant FSH, or TRT with SERMs (e.g. Tamoxifen, Clomiphene) instead of testosterone.
- For couples wishing to conceive : Combination of hCG + recombinant FSH in reproductive medicine
Men planning testosterone therapy should definitely measure their FSH levels beforehand and discuss their options for preserving fertility.
Conclusion
FSH is a key regulatory hormone for male fertility and is often underestimated in the diagnosis of hormonal disorders. It provides valuable clues as to whether the problem lies in the testicles themselves or in their hormonal regulation .
For men who wish to have children, experience loss of libido, or are planning testosterone therapy, a current FSH level is essential as part of a comprehensive hormone check.
Tip: Have your FSH levels checked along with testosterone, LH, and SHBG with the TRT Check from Adon Health – conveniently from home. For more information about testosterone levels, read our blog post on understanding testosterone levels or listen to our podcast episode with Andreas Scholz!
