**5. Male infertility**

The WHO defines infertility as 'the inability of a sexually active, non-contracepting couple to achieve pregnancy in one year [40]. According to the WHO, about 9% of couples worldwide have fertility problems and around 70 million people are regarded as infertile [41]. The male factor varies and many publications contribute a factor of 30–40% to the man, 40% to the woman and the remainder is said to be idiopathic. The production of spermatozoa (spermatogenesis) in the testis and their subsequent maturation to physiological functionality in the epididymis are complex processes that needed to be strictly controlled in a timely and spatial manner. A disturbance of any of the individual steps involved may lead to impaired male fertility.
