## Negative Feedback Control of GnRH in Males **Key Point:** Testosterone is the primary hormone responsible for negative feedback inhibition of GnRH secretion at both the hypothalamic and anterior pituitary levels in males. ### Mechanism of Testosterone Feedback 1. Testosterone acts on GnRH neurons in the hypothalamus to suppress GnRH release 2. Testosterone also acts on gonadotroph cells in the anterior pituitary to reduce sensitivity to GnRH and decrease LH secretion 3. This dual-level feedback maintains homeostatic control of the hypothalamic-pituitary-gonadal (HPG) axis ### Role of Other Hormones | Hormone | Primary Function | Feedback Role | |---------|------------------|---------------| | Testosterone | Androgen; male sexual development | Negative feedback on GnRH and LH | | FSH | Stimulates spermatogenesis | Primarily regulated by inhibin feedback | | Inhibin | Produced by Sertoli cells | Selective negative feedback on FSH | | hCG | Placental hormone in pregnancy | Not involved in male HPG axis feedback | **High-Yield:** The HPG axis operates on a negative feedback loop where testosterone suppresses its own production by inhibiting GnRH and LH secretion. This is distinct from the positive feedback seen with estrogen in females during the ovulatory surge. **Clinical Pearl:** Exogenous testosterone administration suppresses endogenous LH and FSH, leading to testicular atrophy and infertility — a principle used in hormonal contraception and relevant to anabolic steroid abuse.
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