1. What is male sterility?
  2. What are the possible genetic causes of male sterility?

What is male sterility?

Male sterility corresponds to a reduced reproductive capacity in men and contributes for 50% to sterility in couples. The condition of male sterility is determined when certain conditions occur, like for example azoospermia, that is the total absence of spermatozoids, criptozoospermia, which indicates a drastic lack of spermatozoids in seminal fluid, anejaculation, that is the absence of ejaculation, or necrozoospermia that occurs when the spermatozoids present in seminal fluid are dead. Sterility is defined as primary when a man has never been able to induce a pregnancy, and secondary when instead he has previously been able to do so. There are different causes of sterility: anatomical, infectious, hormonal and genetic.

What are the possible genetic causes of male sterility?

In case of reduced or absent production of spermatozoids, the cause usually lies in imperfect testicular development due to a possible genetic predisposition. Genetic anomalies contribute by 15-30% to male sterility. 5-7% of genetic causes is represented by anomalies in chromosomes and in particular aneuploidies, term that indicates the presence of an incorrect number of chromosomes. Klinefelter syndrome is a chromosomal abnormality affecting men and is characterised by the presence of three sex chromosomes (XXY instead of XY). This syndrome may cause a halt in spermatogenesis determining sterility but even though it also causes testosterone levels to be low, libido does not disappear. Another type of chromosomal abnormality is translocations. An example is Robertsonian translocations that influence fertility of 1 men on 1000 and consists in the merger of two chromosomes that leads these individuals to have one additional copy (trisomy) of a certain chromosome or one copy less (monosomy). In this situation sterility only depends on the decreased chances of the formation and implantation of a vital embryo.