Male reproductive physiology: the hypothalamic-pituitary-testicular axis
How pulsatile GnRH drives LH to Leydig cells and FSH to Sertoli cells, why intratesticular testosterone matters for sperm, how SHBG, aromatase and 5α-reductase shape testosterone results, and how to read a gonadotrophin pattern in obesity, Klinefelter syndrome, anabolic steroid use and androgen deprivation therapy.
Tier 2Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Pulsatile GnRH (every 60 to 120 minutes) drives LH and FSH. Kisspeptin neurons in the arcuate nucleus generate the pulses. Continuous GnRH shuts the axis down.
- LH to Leydig cells makes testosterone. FSH to Sertoli cells, with high intratesticular testosterone, makes sperm.
- Testosterone (directly and after aromatisation to oestradiol) feeds back on LH. Inhibin B feeds back on FSH alone.
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Sources
- Williams Textbook of Endocrinology, 15th editionElsevier (Melmed S, Auchus RJ, Goldfine AB, Rosen CJ, Kopp PA, editors), 2024
- Yeap BB, Grossmann M, McLachlan RI et al. Endocrine Society of Australia position statement on male hypogonadism (part 1): assessment and indications for testosterone therapy. Med J Aust 2016;205:173-8Endocrine Society of Australia, 2016
- Bhasin S, Brito JP, Cunningham GR et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2018;103:1715-44Endocrine Society, 2018
- Lincoff AM, Bhasin S, Flevaris P et al. Cardiovascular safety of testosterone-replacement therapy (TRAVERSE). N Engl J Med 2023;389:107-17New England Journal of Medicine, 2023
- Wittert G, Bracken K, Robledo KP et al. Testosterone treatment to prevent or revert type 2 diabetes in men enrolled in a lifestyle programme (T4DM). Lancet Diabetes Endocrinol 2021;9:32-45The Lancet Diabetes and Endocrinology, 2021
- WHO laboratory manual for the examination and processing of human semen, 6th editionWorld Health Organization, 2021
- Last updated
- 14 November 2026
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