Genetic causes of nonobstructive azoospermia
Hypergonadotropic hypogonadism (elevated FSH with low testosterone) is due to testicular failure in both the endocrinological and spermatogenic functions. flovent inhaler
Various acquired conditions listed in Table 1 are associated with hypergonadotropic hypogonadism. The most well known congenital or genetic cause of hypergonadotropic hypogonadism is Klinefelter’s syndrome. Occurring in one in 500 live male births and accounting for 14% of cases of azoospermia , Klinefelter’s syndrome is the most commonly encountered chromosomal abnormality in male infertility. The chromosomal constitution of the classic form is 47 XXY (90% of cases), whereas that of the mosaic form is 46 XY/47 XXY. The fertility prognosis is better in the mosaic form, and natural fecundity in such men has been reported.
In addition to 47 XXY in Klinefelter’s syndrome, other common karyotypical abnormalities found in men with nonobstructive azoospermia include translocation of chromosomes, XX male, 45 X/46 XY (mixed gonadal dysgene-sis), 46 XY Noonan’s syndrome and XYY male. Recently, different spermatogenesis loci have been mapped on the Y chromosome and named ‘azoospermia factors’ (AZFa, b, c and d). Deletion of a microsegment of the Y chromosome results in severe testiculopathy leading to male infertility. Y chromosome microdeletion is the most prevalent molecularly definable genetic abnormality in male infertility and is found in 5% to 21% of men with severe oligospermia or azoospermia (see “Genetic risks associated with advanced assisted reproductive technology”, to appear in next issue).