Why men need it for fertility and testicular function
Follicle-stimulating hormone (FSH) belongs to the group of pituitary gonadotropins and is a central regulator of male fertility. Although its name is known from women's medicine, where it stimulates the growth of ovarian follicles, FSH also plays a crucial role in men: it stimulates sperm production in the testicles and ensures the healthy function of Sertoli cells, which are responsible for the development of mature sperm.
An unbalanced FSH level can indicate fertility disorders, hormone deficiency, or disorders of the hypothalamic-pituitary-testicular axis. For men with unfulfilled desire to have children or an abnormal spermiogram, FSH diagnostics are essential, as are in the context of testosterone replacement 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 to the testicles via the bloodstream. 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.
Furthermore, 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 formation
When should FSH be tested in men?
An FSH test is useful for:
- Unfulfilled desire to have children
- Low sperm count or poor sperm quality
- Erectile dysfunction or loss of libido
- Suspected primary testicular failure
- Diagnosis of hypogonadism (testosterone deficiency)
- Before or during testosterone replacement therapy (TRT)
What does a low or high FSH level mean?
Elevated FSH:
An elevated FSH level can indicate primary testicular insufficiency – meaning that the testicles no longer respond adequately to signals from the brain. Possible causes:
- genetic syndromes (e.g., Klinefelter)
- testicular inflammation
- history of 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. Causes can include:
- chronic stress (cortisol inhibits gonadotropin secretion)
- medications such as opiates or anabolics
- very low body fat percentages / excessive training
- tumors or brain injuries
- secondary hypogonadism
If FSH is suppressed by external factors (e.g., by TRT), it can lead to temporary infertility – an aspect that should be absolutely considered before TRT.
How is FSH measured?
FSH is determined in the 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
- Spermiogram (for desire to have children)
- possibly 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 values within the borderline range.
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 (whether medically supervised TRT or abuse)
- Medications and environmental toxins
How can an unbalanced FSH level be treated?
Therapy depends on the cause:
- For primary testicular failure: No direct therapy possible – possibly sperm cryopreservation
- For central hormone suppression: Stress reduction, dietary changes, micronutrients
- For planned TRT: Preserve fertility, possibly TRT in combination with recombinant FSH, or TRT with SERMs (e.g., tamoxifen, clomiphene) instead of testosterone
- For desire to have children: Combination of hCG + recombinant FSH in reproductive medicine
Men planning testosterone replacement therapy should definitely have their FSH level checked beforehand and discuss their options for preserving fertility.
Conclusion
FSH is a central control hormone for male fertility and is often underestimated in the diagnosis of hormonal disorders. It provides valuable information on whether the problem lies in the testicles themselves or in hormonal control.
For men with unfulfilled desire to have children, loss of libido, or planned testosterone therapy, a current FSH value as part of a holistic hormone check is indispensable.
Tip: Have your FSH level checked together with testosterone, LH, and SHBG in the TRT Check by Adon Health – conveniently from home. For more knowledge about testosterone levels, read our blog post on understanding testosterone levels or listen to our podcast episode with Andreas Scholz!