Genetics sometimes play a role in contributing to azoospermia; one study suggested that approximately 6 percent of infertile men had an underlying genetic disorder. While the statistics seem low, it may be worth investigating this route if no other reason for the low sperm count can be found. Simply having the information can help you and the doctor find the best treatment available to prevent passing the defective gene down to future generations. It can also be beneficial to know that the infertility is a result of a genetic defect, and not a preventable behavior, like drug use.
The normal male karyotype is 46XY, meaning that he has one X chromosome and one Y chromosome. One relatively common deviation, occurring in about one in five hundred live male births, is XXY, called Klinefelter's syndrome. Men with this disease typically have small firm testes, obesity, decreased intelligence, and decreased development of secondary sex characteristics. Tests will show that FSH levels are elevated, and estradiol and testosterone levels are either normal or increased. Men with Klinefelter's syndrome don't usually produce much, if any, sperm.
Y Chromosome Microdeletion
The genes for spermatogenesis (the process of making sperm) are found on particular sections of the Y chromosome. If the information available in one or more of these sections is missing, the male will be normal by all appearances but may or may not produce viable sperm, depending on the location of the microdeletion. It is important to know that this genetic abnormality can be passed down to male children, so evaluation is definitely warranted. This can be tested for in a simple blood test. This test is not included in the standard karyotype test, so check with your doctor to see if he is ordering this one as well.