What role does Testosteron play in fertility?

Testosterone is essential for male fertility: it drives spermatogenesis (sperm production) in the testes, promotes sperm maturation in the epididymis, and influences libido and erectile function. Deficiency can impair sperm quality (count, motility, morphology) and lead to infertility. However, the effect is dose-dependent: exogenous testosterone (e.g., supplements or hormone replacement therapy) suppresses endogenous production via the negative feedback loop of the hypothalamic-pituitary-gonadal axis and can worsen fertility. Therefore, testosterone therapy without concomitant gonadotropin stimulation is contraindicated when trying to conceive. In women, testosterone plays a minor but non-negligible role in ovarian function and libido. Evidence is largely based on clinical practice and observational studies; randomized controlled trials on testosterone supplementation for male infertility show conflicting results. A genetic test for testosterone-related genes (e.g., SHBG, AR) provides only weak predictive value and is not diagnostic. Safety note: testosterone supplements without medical supervision can irreversibly impair fertility and increase the risk of cardiovascular events.