If the concentration of testosterone in a man’s blood starts to rise above normal, this system leads to a reduction in testosterone. How does this occur?

Students are aware of the Hyothalamus-pituitary axis (HPA axis) in the female, but are not as aware about the role of the HPA axis in the male reproductive system. Here,we should start off by explaining the normal HPA axis;the hypothalamus releases GnRH, which stimulates the pituitary to release LH and FSH which then stimulate the testes to release testosterone. This is an example of a positive feedback loop. When testosterone increases in the blood, it inhibits GnRH release from the hypothalamus.This will mean less LH and FSH is released from the pituitary (the pituitary itself will also be inhibited) and therefore, there is no stimulation of the testes to produce testosterone. This is an example of a negative feedback loop.