What are the effects of exogenous testosterone on male fertility?

Exogenous Testosterone Severely Impairs Male Fertility and Should Be Avoided in Men Desiring Paternity

For males interested in current or future fertility, clinicians should not prescribe exogenous testosterone therapy. 1 This is a clear, unequivocal recommendation from the most recent 2024 AUA/ASRM Male Infertility Guidelines.

Mechanism of Fertility Impairment

Exogenous testosterone administration provides negative feedback to the hypothalamus and pituitary gland, resulting in:

• Inhibition of gonadotropin secretion (LH and FSH suppression) 1, 2
• Suppression of intratesticular testosterone production 1, 3
• Decreased or complete cessation of spermatogenesis 1, 4
• Oligospermia or azoospermia depending on the degree of testosterone-induced suppression 1, 2

The FDA drug label explicitly states: "At large doses of exogenous androgens, spermatogenesis may also be suppressed through feedback inhibition of pituitary follicle stimulating hormone (FSH)" 3

Recovery Timeline and Prognosis

While most azoospermic males will recover sperm production after cessation of testosterone therapy, critical caveats exist 1:

• Recovery time is prolonged and unpredictable: months to rarely years 1
• Not all patients will recover or tolerate symptoms of low testosterone during the interim 5
• Recovery cannot be guaranteed in terms of timing or whether sperm count will be sufficient for fertility 6

Clinical Decision Algorithm

For Men Planning Near-Term Paternity:

Absolutely avoid exogenous testosterone 1

For Men Planning Distant Future Paternity:

Testosterone therapy may be offered only with comprehensive counseling about:

• Inhibitory effects on spermatogenesis 1
• Prolonged time course required for recovery after cessation 1
• Possibility of incomplete or absent recovery 5, 6

For Men with Hypogonadism Desiring Fertility Preservation:

Use alternative therapies that stimulate endogenous testosterone production rather than exogenous testosterone 4:

• Human chorionic gonadotropin (hCG): 500-2500 IU, 2-3 times weekly 1

  • First-line for hypogonadotropic hypogonadism 1
  • Only FDA-approved option for males among these alternatives 4
  • Add FSH injections after testosterone normalizes on hCG if needed 1

• Selective estrogen receptor modulators (SERMs) 4

• Aromatase inhibitors (AIs) 4

• These agents may be used separately or in combination 4, 2

Critical Pitfalls to Avoid

Common misconception: Many men using exogenous testosterone, particularly for non-medical purposes (bodybuilding, performance enhancement), are unaware of fertility consequences 5, 7, 8. This represents a growing public health concern, especially among young men 8.

Formulation matters: Long-acting testosterone formulations appear to cause more severe and prolonged suppression compared to short-acting formulations 9. Long-acting testosterone resulted in:

• Longer time to pregnancy (33 vs 23 days in controls) 9
• Smaller testicular weight 9
• Nearly undetectable LH levels at 3 months 9

Testicular changes: Men should be counseled that testicular size and consistency often diminish during testosterone therapy, and fertility will be greatly compromised due to gonadotropin down-regulation 10, 3

Preventive Strategies

For men who must use testosterone but wish to preserve fertility potential:

• Consider short-acting testosterone formulations over long-acting 9
• Incorporate low-dose hCG concurrently to maintain intratesticular testosterone and preserve spermatogenesis 11
• Bank sperm before initiating therapy when possible 1

The evidence is unambiguous: exogenous testosterone is gonadotoxic and should be treated with the same fertility preservation counseling as cancer chemotherapy 1.