How does taking testosterone affect fertility?

How Testosterone Lowers Fertility

Exogenous testosterone should never be prescribed to men interested in current or future fertility because it suppresses spermatogenesis through negative feedback on the hypothalamus and pituitary gland, inhibiting gonadotropin secretion and potentially causing complete azoospermia. 1, 2

Mechanism of Fertility Suppression

Testosterone acts as a contraceptive through a well-defined hormonal pathway:

• Negative feedback inhibition: Exogenous testosterone provides negative feedback to the hypothalamus and pituitary gland, which directly inhibits the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). 1, 2, 3, 4, 5

• Loss of intratesticular testosterone: This suppression of LH eliminates the signal for Leydig cells to produce testosterone within the testes, causing intratesticular testosterone levels to plummet despite normal or elevated serum testosterone from the exogenous source. 1

• Spermatogenesis failure: FSH and intratesticular testosterone are both essential for normal sperm maturation—without these signals, developing sperm cannot complete maturation, leading to progressively declining sperm counts. 1, 4, 5

• Progression to azoospermia: Depending on the degree of testosterone-induced suppression, spermatogenesis may decrease or cease altogether, resulting in oligospermia (low sperm count) or complete azoospermia (zero sperm in ejaculate). 1, 2, 3

Clinical Severity and Guideline Recommendations

The 2024 AUA/ASRM Male Infertility Guideline classifies the recommendation against testosterone use in fertility-seeking men as a Clinical Principle—the highest level of directive guidance, indicating this is an absolute contraindication. 2

• Complete suppression is possible: Testosterone can cause complete azoospermia, not just reduced counts—this is severe enough that testosterone has been studied as a male contraceptive. 2, 4, 5

• FDA labeling confirms: The FDA drug label explicitly states that "during treatment with large doses of exogenous androgens, including testosterone gel, spermatogenesis may be suppressed through feedback inhibition of the hypothalamic-pituitary-testicular axis" and warns that "reduced fertility is observed in some men taking testosterone replacement therapy." 3

• Animal data supports mechanism: Nonclinical studies demonstrate that exogenous testosterone administration suppresses spermatogenesis in rats, dogs, and non-human primates, which was reversible upon cessation of treatment. 3

Recovery Timeline and Irreversibility Risk

A critical pitfall is assuming rapid recovery after stopping testosterone:

• Prolonged recovery: Although recovery of sperm to the ejaculate occurs in most azoospermic males after cessation of testosterone therapy, the time course may be prolonged—taking months or rarely years. 1, 2

• Potential irreversibility: The FDA label warns that "with either type of use, the impact on fertility may be irreversible," particularly in men who abuse anabolic steroids, with documented cases of testicular atrophy, subfertility, and permanent infertility. 3

• Avoid in near-term fertility planning: Exogenous testosterone therapy should be completely avoided in males pursuing or planning to pursue family building in the near future. 1, 2

Formulation-Specific Suppression Patterns

Different testosterone preparations vary in their degree of gonadotropin suppression:

• Long-acting injectables (enanthate, undecanoate) decrease FSH by 86.3% and LH by 71.8%. 6

• Intermediate-acting daily gels/patches decrease FSH by 60.2% and LH by 59.2%. 6

• Short-acting intranasal preparations decrease FSH by 37.8% and LH by 47.3%. 6

However, all formulations suppress spermatogenesis to some degree, and even the "less suppressive" short-acting preparations still significantly impair fertility. 6

Alternative Approaches for Hypogonadal Men Desiring Fertility

For men with true hypogonadism who need testosterone optimization while preserving fertility:

• Human chorionic gonadotropin (hCG) is the first-line treatment for hypogonadotropic hypogonadism, administered as injections (500-2500 IU, 2-3 times weekly) to stimulate endogenous testosterone production without suppressing spermatogenesis. 1, 2

• FSH injections may be added after testosterone levels normalize on hCG if sperm production remains inadequate. 1

• Selective estrogen receptor modulators (SERMs) such as clomiphene citrate and aromatase inhibitors can increase endogenous testosterone production through different mechanisms without directly suppressing the HPG axis. 2, 7

Common Clinical Pitfalls to Avoid

• Never assume testosterone is safe for fertility: This is the single most important clinical principle—testosterone is a contraceptive and should be treated as such. 2, 4

• Don't prescribe testosterone for "low normal" testosterone in fertility-seeking men: Even men with borderline low testosterone should avoid exogenous testosterone if fertility is a consideration. 1, 2

• Counsel about delayed recovery: Patients must understand that stopping testosterone doesn't immediately restore fertility—recovery can take many months to years, and some men may never fully recover. 1, 2, 3

• Consider sperm banking: If a patient is already on testosterone and may want future fertility, sperm banking should be offered immediately before further suppression occurs. 2