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Genetic Diagnosis of Male Infertility

Genetic abnormalities cause infertility by affecting the sperm production and transfer. The male infertility and the content of its treatment has recently made it necessary to use genetic diagnosis methods. The requirement of the tests intended for the most frequently seen problems are listed among the routine examinations. While the numerical abnormalities in the chromosomes deteriorate the testicular functions, the regional microdeletions in Y chromosome may cause hesitations during the sperm production process. In addition, some single gene disorders; for example, a mutation in the CFTR gene associated with Cystic Fibrosis, are associated with the absence of the intra-testicular ducts.

Chromosomal Abnormalities:

The frequency of all chromosomal abnormalities in infertile males has been reported to be approx. 7%. This is inversely proportional to the sperm concentration. That’s this rate is at the highest level (10-15%) in the azoospermic males (those who do not have any spermatozoa in the semen). It is seen at a rate of 5% in the oligospermic males (those who have less than the normal number of spermatozoa in the semen). In those males with normal number of spermatozoa, this rate is less than 1%. The most frequently seen chromosomal abnormality in infertile males is the Klinefelter Syndrome ( 47 XXY; 46 XY/47XXY). It constitutes the two third of the chromosomal abnormalities in the infertile males. Therefore, in case of azoospermia not associated with obstruction or severe oligospermia, a karyotyping, that’s a chromosome test, should be performed on a blood sample received from the arm of the patient.

Y Chromosome Microdeletions:

It is the Y chromosome that enables the sex to be determined as male. The very smallest losses within some of the regions on Y chromosome are called microdeletion. These microdeletions cannot be determined using standard chromosome tests. For this,more sophisticated genetic tests should be used. These tests can be also performed on a simple blood sample received from the arm. Microdeletion is found in the Y chromosome of 7-10% of azoospermic and severely oligospermic infertile males. These losses usually seen in the long arm of the chromosome includes the necessary genes required for normal sperm production such as AZF (Azoospermic Factor)a, AZFb and AZFc, etc. The microdeletions within these regions cause the loss of function of the gene codes, that’s pauses in sperm production. The males with microdeletion within AZFc region is only severely oligospermic, and sperm can be found in the testicles of many of these males through surgical methods. The possibility of finding sperm is highly low in the males found to have microdeletion within AZFa and AZFb regions. It is likely for those males with Y chromosome microdeletion to pass this disorder and its clinical results to their sons. For the in-vitro fertilization to be made to these patients, performing preimplantation genetic diagnosis (PGD) of the embryos prior to the transfer will prevent this case.