Everybody knows about female menstrual cycle. Would you know men also have a cycle ?
This cycle called spermatogenesis is a 75 days period which is the required duration for sperm cells maturation and production. As the spermatogenesis is a permanent and continuous phenomenon the cycle cannot normally be noticeable. Here is how it works :
On the male mammals side, spermatogenesis takes place inside the testes which Nature located outside the body in a pouch called scrotum. From this simple fact accompagnied with a special blood circulation mechanism inside the scrotum testes are maintained several degrees cooler than normal body temperature . Those features induce two functional modes for spermatogenesis :

• it is enable when testes temperature is under a threshold below human body temperature (by 3 to 4 celsius degrees).

• it is disable when testes temperature raises above the threshold during repetitive periods. This puts on hold the sperm cells production.

What's interesting to notice is that testes are the only fonctional organ directly reachable from outside the body, as if a way has been provided to access to male contraception...