An understanding of the hypothalamic-pituitary-gonadal axis is vital for the management of men with infertility and erectile dysfunction (ED). The commonly encountered hormones include—
• LHRH—luteinizing hormone releasing factor
• LH—luteinizing hormone
• FSH—follicle-stimulating hormone
Pulses of LHRH from the hypothalamus stimulate LH and FSH release from the anterior pituitary.
• LH stimulates testosterone production from Leydig cells of the testis
• FSH stimulates Sertoli cells in the seminiferous tubules to produce mature sperm
• Production of inhibin is increased by FSH release, and this effects a negative feedback to the pituitary to decrease FSH release
• Locally (within the testis to aid spermatogenesis)
• Systemically (to produce male secondary sexual characteristics, anabolism, and libido)
• To have a negative feedback on the hypothalamus/pituitary to inhibit LHRH secretion.
Prolactin (produced by the anterior pituitary)—
• Role in men not completely understood
• Thought to increase concentration of LH receptors in Leydig cells (and therefore increase testosterone levels)
• Enhances the effects of testosterone and helps maintain libido
Table 2.8 highlights some of the common features related to sex hormones in males.
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