HPTA axis & fertility

The hypothalamic–pituitary–testicular axis, testosterone production, spermatogenesis, suppression, and recovery.

L1Fundamentals

4 modules · exam at 85%

1.1
The HPTA axisSimulatorfree lesson
GnRH, LH and FSH, Leydig and Sertoli cells, intratesticular testosterone, inhibin B.
1.2
How testosterone is madePathwaymembers
Steroidogenesis from cholesterol, and what regulates each step.
1.3
SpermatogenesisTimelinemembers
The ~74-day cycle, what it depends on, and why changes show up months later.
1.4
Estradiol in menmembers
Aromatase, what E2 does in men, its role in feedback, and prolactin.

5 modules · exam at 85%

2.1
Binding proteins and free hormoneLab readermembers
SHBG as a moving variable, the free-fraction cascade, and why a normal total can mislead.
2.2
Suppression and recoverySimulatorincoming
Why outside androgens shut the axis down and what slows its return.
2.3
Fertility testing and sperm qualityLab readermembers
Semen analysis, DNA fragmentation, oxidative stress, and hormone panels.
2.4
Protecting fertilityincoming
Sperm banking and when to see a reproductive urologist.
2.5
Diagnosing hypogonadismincoming
Repeat morning testing, primary vs secondary, and finding the cause.

4 modules · exam at 85%

3.1
Neuroendocrine controlincoming
Kisspeptin, GnRH pulse frequency, and where feedback really lands.
3.2
Leydig cell biologyincoming
LH signaling, desensitization, and capacity loss over time.
3.3
The recovery evidenceincoming
What human studies show about long-term recovery and who doesn’t recover.
3.4
Case analysisincoming
Work through a two-panel case from mechanism to next steps.

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