Azoospermia accounts for approximately one-sixth of cases of male infertility. Commonly referred to as ‘no sperm count’, men suffering from this condition are unable to father a child. Azoosperma may arise because there is a failure to product sperm. Or, in some cases there is a blockage that prevents the sperm from entering the ejaculate.
The causes of azoospermia are numerous and may include:
- Cancer treatment (chemotherapy, radiation, surgery)
- Congenital adrenal hyperplasia
- Diabetes mellitus
- Ejaculatory duct obstruction
- Genetic infertility due to abnormal chromosomes (karyotype)
- Hypothalamic/pituitary tumor
- Obstruction, congenital absence of the vas deferens (CAVD)
- Pesticide/toxin exposure (including hot tubs and baths)
- Pituitary suppression, drug induced (anabolic steroids, alcohol, glucocorticoids)
- Primary testicular failure, Klinefelter syndrome
- Scrotal trauma or surgery
- Secondary testicular failure, Kallman syndrome
- Severe illness (cancer, kidney or liver failure)
- Sickle cell anemia
- Sperm autoimmunity
- Testosterone supplements
- Un-descended testicles at birth
- Unexplained genetic infertility
- Unexplained gonadotropin deficiency
- Varicocele effect
- Y chromosome microdeletions
- Young syndrome
Now researchers in Pennsylvania have found another link to azoosperma.
X-chromosome gene may hold the key to treating some forms of azoospermia
Yang and colleagues have been investigating a gene on the X chromosome known as TEX11. This gene is responsible for chromosomal synapsis and meiotic recombination. These researchers have found that this gene is often mutated in men with non-obstructive azoospermia. A large scale genetic screening of idiopathic infertile men revealed the mutations of the TEX11 gene were responsible for 1% of azoospermia.
Interestingly, when a non-mutated TEX11 gene was introduced into mice that were bred to lack the gene, fertility was restored. What researchers discovered was that there’s a certain amount of protein produced by the TEX11 gene that’s needed to enable sperm to develop. This protein is influential in arranging chromosomes during sperm cell division. Therefore, if this gene is absent or mutated, the body is unable to produce sperm.
What are the implications of these latest findings?
This research may have important implications for identifying and treating certain azoospermia cases in men. Screening patients for TEX11 genetic mutations may help to narrow down the cause of non-obstructive azoospermia. If an abnormality of this gene is identified, then it provides clarity as to the cause of infertility.
With advances in genetic research and technologies, treating problems such as mutations may be possible. In the meantime, having clarity surrounding the cause of azoospermia can help couples to make more informed decisions regarding their reproductive health. This may make it easier to commit to assisted reproduction treatments, such as IVF.
Yang, F., Silber, S., Leu, N. A., Oates, R. D., Marszalek, J. D., Skaletsky, H., Brown, L. G., Rozen, S., Page, D. C. and Wang, P. J. (2015), TEX11 is mutated in infertile men with azoospermia and regulates genome-wide recombination rates in mouse. EMBO Mol Med. doi: 10.15252/emmm.201404967.