Exogenous Testosterone Suppresses LH/FSH Output
Placeholder: external testosterone tricks the pituitary into slowing hormone release.
- Hypothalamus: Feedback sensed at (Placeholder short note)
- LH & FSH: Primary hormones cut (Placeholder short note)
- Weeks: Onset of suppression (Placeholder short note)
- Injection/gel: Common therapy route (Placeholder short note)
How exogenous testosterone signals the brain
Placeholder: circulating testosterone is read as a signal to reduce natural production.
Why fertility is affected early
Placeholder: LH and FSH normally drive testicular sperm production.
HPG Axis Negative Feedback Loop Shuts Down
Placeholder: the hypothalamic-pituitary-gonadal axis quiets its normal pulsatile signaling.
- Reduced: GnRH pulse amplitude (Placeholder short note)
- Near-zero: Pituitary LH output (Placeholder short note)
- Falls sharply: Intratesticular T (Placeholder short note)
- ~3 months: Time to full shutdown (Placeholder short note)
The feedback loop mechanics
Placeholder: high peripheral testosterone dampens GnRH pulsing upstream.
Consequence for local testicular hormone levels
Placeholder: intratesticular testosterone drops despite normal blood levels.
Spermatogenesis Declines, Raising Infertility Risk
Placeholder: sperm production slows as testicular stimulation disappears.
- 3–6 mo: Time to oligospermia (Placeholder short note)
- Up to ~90%: Azoospermia incidence (Placeholder short note)
- Decreases: Testicular volume (Placeholder short note)
- Progressive drop: Sperm count trend (Placeholder short note)
Testicular tissue changes over time
Placeholder: seminiferous tubules shrink without FSH/LH stimulation.
Clinical infertility implications
Placeholder: many men on therapy become temporarily infertile.
Reversibility Timeline After Stopping Therapy
Placeholder: fertility often recovers gradually once therapy is discontinued.
- ~4–12 mo: Median recovery time (Placeholder short note)
- Most patients: Full recovery cases (Placeholder short note)
- Longer duration: Factors slowing recovery (Placeholder short note)
- Uncommon: Rare permanent cases (Placeholder short note)
What drives recovery speed
Placeholder: duration of therapy and age influence recovery pace.
Monitoring recovery
Placeholder: semen analysis tracks the return of sperm production.
hCG and SERMs Help Preserve Fertility
Placeholder: co-therapies can keep testicular signaling active during treatment.
- LH activity: hCG mimics (Placeholder short note)
- Clomiphene/tamoxifen: SERM examples (Placeholder short note)
- Recommended: Sperm banking option (Placeholder short note)
- Before starting therapy: Counseling timing (Placeholder short note)
How hCG co-therapy works
Placeholder: hCG directly stimulates testicular Leydig cells like LH would.
Placeholder: discuss fertility goals with a clinician before starting therapy.
Alternative options for patients
Placeholder: SERMs and sperm banking are common preservation strategies.