Causes of Nonobstructive Azoospermia

There are numerous causes of nonobstructive azoospermia:

• Genetics
• Y Chromosome deletion
• Karyotype abnormality
• Radiation and toxins 
• Medications
• Hormone imbalances
• Varicocele

Other cases of nonobstructive azoospermia include Illegal drug use, excessive drinking and smoking.

Genetics

Not all genetic causes of impaired sperm production are understood yet, but it is a field we study and watch closely. It is important to understand that: 

Causes that are known and diagnosable can help guide your treatment, with a better likelihood of finding hidden sperm for some conditions than others.

You risk passing genetic mutations to children, so our genetic counselors help guide you through those important decisions.

Y Chromosome Deletion

The Y chromosome contains many genes that are critical for sperm production, but some men are missing crucial sections. Y chromosome deletions cause up to 10 percent of azoospermia cases, so we carefully screen for this possibility. In fact, one of our advisors (Dr. Renee Reijo Pera) was the first investigator to identify the importance of these genes in sperm production. 

The diagnosis of a specific Y chromosome problem is important, since certain deletions (e.g., AZFc) carry a better likelihood for finding sperm.

Any sons born to fathers with Y chromosome deletions will inherit the defect.

Karyotype abnormality

Men normally have 46 chromosomes: Pairs numbering 1 through 22 for a total of 44, plus an X and a Y. But up to 10 percent of nonobstructive azoospermia patients have detectable abnormalities that can limit sperm production. An extra X chromosome causes Klinefelter syndrome, characterized by poor testicular function as well as low sperm counts and testosterone levels. But we are still often able to find some sperm in such cases.

Radiation and toxins

Certain exposures can impair sperm production:

Some toxic chemicals (with possible links to pesticides)

• Heavy metals
• Chemotherapy
• Radiation therapy

If you plan to undergo chemotherapy or radiation treatment, it is often a good idea to freeze (cryopreserve) sperm ahead of time. But we are still often able to find sperm after such cancer treatments.

Medications

Several medications can harm sperm production, so we help you decide which, if any, you want to continue using. Testosterone is one example: While the hormone is necessary for normal reproductive function, taking it in supplemental form can often cause azoospermia.

Hormone imbalances

It is possible that an imbalance of hormones is causing your azoospermia, and we can treat the problem.

Varicocele

Veins in the scrotum may become enlarged and widened, forming a varicocele and impairing normal sperm production. Learn more about varicocele care through our partner, the Male Reproductive Medicine and Surgery Program.