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How the Gonadal Axis Works

How the Gonadal Axis Works

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What is the gonadal axis?

The gonadal axis involves a complex interaction between the hypothalamus, pituitary gland and the gonads. This axis helps to regulate development, reproduction, ageing and many other key physiological processes.

How the male gonadal axis works

1. The hypothalamus secretes GnRH.

2. GnRH travels down to the anterior pituitary gland and binds to receptors on the gland.

3. This promotes the release of LH (luteinizing hormone) and FSH (follicle-stimulating hormone).

4. LH and FSH travel in the bloodstream to the testicles.

5. LH stimulates Leydig cells in the testicles to produce testosterone (testosterone is required for spermatogenesis and many other important biological processes).

6. FSH stimulates Sertoli cells to produce androgen binding globulin (ABG) and inhibin:

       
  • Androgen binding globulin is a protein that binds to testosterone and prevents it from leaving the seminiferous tubules
  •    
  • Inhibin helps support spermatogenesis and inhibits the production of FSH, LH and GnRH

7. Increased levels of testosterone and inhibin have a negative feedback effect on the pituitary and hypothalamus.

8. This results in decreased production of LH and FSH.

9. As a result, the production of testosterone and inhibin is also decreased.

How the Female Gonadal Axis Works

1. The hypothalamus releases GnRH.

2. GnRH travels to the anterior pituitary gland and binds to receptors on the gland.

3. This stimulates the secretion of LH (luteinizing hormone) and FSH (follicle-stimulating hormone).

4. LH and FSH travel through the bloodstream to the ovaries.

5. When LH and FSH bind to the ovaries, they stimulate the production of oestrogen and inhibin:

       
  • Oestrogen helps manage the menstrual cycle and is essential to many other physiological processes.
  •    
  • Inhibin inhibits activin, which generally stimulates GnRH production.

6. As the levels of oestrogen and inhibin rise, they have a negative feedback effect on the pituitary and hypothalamus.

7. This causes a decrease in the production of GnRH, LH and FSH.

8. This, in turn, reduces the production of oestrogen and inhibin.

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