What is female sterility?
Sterility is defined as the inability to conceive and can affect both men and women. Primary sterility is when a couple has never been able to conceive while secondary sterility is when a couple has previously been able to do so. In addition, sterility in couples is related to the combined characteristics of a couple. The causes of female sterility are multiple, like genetic, anatomical, hormonal, and infectious.
What are the possible genetic causes of female sterility?
Genetic causes of female sterility are distinguished in genetic (dependant on genes) and chromosomal (dependant on chromosomes). Genetic defects include Kallmann syndrome, which is characterised by the association of two specific clinical manifestations: absent or partial development of genitalia (hypogonadism) associated to sterility, and partial or total loss of the sense of smell.
Chromosomal abnormalities instead cause over 52% of spontaneous abortions and therefore can potentially cause sterility. These abnormalities can be congenital, if present since birth; an example is Turner syndrome, which is caused by a chromosomal abnormality in which one of the X chromosomes is absent or altered, totally or partially. People affected by this syndrome usually have 45 chromosomes instead of 46 and this leads to the absence of the normal ovarian function and therefore to the inability to produce oocytes. Another example of chromosomal abnormality is Morris syndrome (androgen insensitivity syndrome – AIS), which involves a male chromosomal composition associated to a female body and aspect. There can also be damages of the chromosomal structure, known as “Robertsonian translocations”, in which two chromosomes come together, both losing a part. This means that the two chromosomes remain attached to each other and the gametes of these individuals will be carriers of either an additional copy (trisomy) of a certain chromosome or of one copy less (monosomy). Translocations cause an increase in the risk of spontaneous abortion.
- However, the incidence of these syndromes is quite low:
- Kallmann syndrome = 1 woman in 50000
- Turner syndrome = 1 woman in 2000/2500
- Morris syndrome = 1 woman in 13000