Testosterone replacement therapy suppresses spermatogenesis by inhibiting gonadotropins and reducing intratesticular testosterone, with variable recovery kinetics after cessation, though medical therapies and short-acting formulations may preserve or restore sperm production in select populations.
The mechanism involves suppression of the hypothalamic-pituitary-gonadal (HPG) axis.
Both LH and FSH are suppressed by exogenous androgen administration.
Intratesticular testosterone, which is critical for spermatogenesis, is drastically reduced.
This represents the primary contraindication to TRT use in men trying to conceive.
Background
Sperm production often slowly resumes after TRT cessation, but recovery shows highly variable kinetics that might complicate family planning.
Recovery of spermatogenesis following TRT discontinuation is not guaranteed to be complete or timely.
The variability in recovery rate is described as potentially complicating family planning for men who used TRT.
The paper characterizes recovery as 'often slowly resumes,' indicating it is not a rapid process.
Background
Medical therapies including aromatase inhibitors and selective oestrogen receptor antagonists may be used to preserve or restore spermatogenesis in select populations receiving TRT.
These agents work by modulating estrogen signaling to support endogenous gonadotropin production.
They are identified as options for men receiving TRT who wish to preserve fertility.
Use is described as appropriate for 'select populations,' indicating not universal applicability.
Background
Exogenous gonadotropins including human chorionic gonadotropin (hCG) and follicle-stimulating hormone (FSH) may be used to preserve or restore spermatogenesis in men on TRT.
hCG can mimic LH activity to stimulate intratesticular testosterone production.
FSH supplementation addresses the FSH-dependent aspects of spermatogenesis.
These are described as options for 'select populations receiving TRT.'
Background
New short-acting testosterone formulations, including oral testosterone undecanoate and nasal testosterone gel, may incompletely suppress the HPG axis and partially preserve spermatogenesis.
Oral testosterone undecanoate is identified as one such short-acting formulation.
Nasal testosterone gel is identified as another short-acting formulation.
These formulations are described as causing 'incomplete' rather than complete suppression of the hypothalamic-pituitary-gonadal axis.
The result is described as 'partial' preservation of spermatogenesis, not complete preservation.
Exogenous testosterone remains contraindicated in men actively trying to conceive despite these newer options.
Background
The prevalence of symptomatic, laboratory-proven testosterone deficiency increases with age and is often treated with testosterone replacement therapy.
Testosterone deficiency is defined as both symptomatic and laboratory-proven.
The condition's prevalence is age-dependent.
TRT is described as a common treatment for this condition.
The intersection of testosterone deficiency treatment and reproductive-age men creates clinical complexity around fertility preservation.
Background
Testosterone has a pivotal role in spermatogenesis, erectile function, libido, and expression of secondary sexual characteristics.
Spermatogenesis is specifically dependent on adequate testosterone levels, particularly intratesticular testosterone.
Multiple physiological functions beyond reproduction are dependent on testosterone.
This multifaceted role underlies the clinical rationale for TRT despite its reproductive side effects.