KARYOTYPE
This is a study of the number and the structure of the chromosomes present in the nuclei of cells. It involves extraction of blood.
Each cell of the body should have a total of 46 chromosomes, organised into 22 pairs of autosomes and 1 pair of allosomes, which determine gender. The only cells of the body that contain half the chromosomes (23) are eggs and spermatozoa, because when they join to form the embryo, together they add up to a total of 46 chromosomes.
An alteration in a patient’s karyotype increases the risk of gametes (spermatozoa) with an anomalous genetic load. This increases the production of embryos with genetic problems and prompts cases of sterility or recurrent miscarriages
SPERM DNA FRAGMENTATION
This is the study of the genetic material of the spermatozoa in the ejaculate. It is a parameter that is independent from and complementary to traditional tests such as semen analysis.
DNA may sometimes have break points or losses of genetic material in the DNA chains of the spermatozoon. The more break points there are, the worse the prospects of reproduction, as the embryos generated with these sperm will more likely be of a lower quality and/or will have low implantation potential. In some cases, such damage may be repaired by the egg, although this mainly depends on its quality. Hence, the greater the oocyte quality, the higher the capacity to repair sperm damage.
Different factors may cause fragmentation. They are classified as follows:
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Internal factors (primary fragmentation)
Fragmentation is caused by abnormal maturation of spermatozoa in the epididymis, or because the control mechanisms in the testicle do not work properly, are unable to eliminate these abnormal sperm and allow them to continue to ejaculation. This could explain why there is a greater incidence of DNA fragmentation in men of over 45 years old.
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External factors (secondary fragmentation)
Several factors may induce DNA breakage. They may be either pathological (cancer, inflammatory processes, varicoceles, cryptorchidism or stress) or external factors (such as pollution, tobacco, some drugs, advanced age or metabolic alterations due to excess weight). In some cases, damage is permanent: for example after radiotherapy or chemotherapy treatments. In others it may be temporary, as is the case of testicular varicocele, exposure to high temperatures (either for occupational causes or as a result of an episode of high fever), inflammatory processes and/or infectious testicular processes (orchitis).
A fragmentation test is recommended in the following cases:
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Varicocele
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Cryptorchidism
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Serious seminal factor
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Chemotherapy
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Diabetes mellitus
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Idiopathic sterility
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Recurrent miscarriages
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Recurrent IVF failure
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Exposure to toxic substances or to high temperatures
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BMI > 25
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Age > 45 years old
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Smokers ( >10 c/day)
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Alcohol ( > 6 units/week)
FISH
FISH (fluorescent in situ hybridisation) is a molecular cytogenetic technique based on the hybridisation of two chains of DNA when their sequence is complementary.
It is a sensitive method for evaluating the normal chromosomal complement of a cell.
FISH in spermatozoa is suitable in those patients with abnormal karyotypes, alterations of meiosis and abnormalities in the semen.
Genetic and chromosomal anomalies could cause sterility or infertility because of alteration in the production of spermatozoa or of alteration in seminal tracts and, therefore, in the transport of the sperm.
One characteristic of this technique, however, is that it only allows for the study of a limited number of chromosomes. Normally, a study of 5 chromosomes is required: X, Y, 13, 18 and 21. It may therefore yield a normal result in those chromosomes that have been studied, but show chromosomal anomaly in others. It is also of limited use in patients with a low sperm count, as this technique cannot yield a result because of a lack of material. To perform it, a sperm count should contain at least one million spermatozoa/ml.
OTHER
In the event of dysfunctional sexual relations, testicular pain or the suspected presence of varicoceles, an andrologist should be consulted.