Y Chromosome Microdeletions

Is Testing Right for Me? I Have My Test Results

Y Chromosome Microdeletions

Y Microdeletions and Male Infertility

Normal male development depends on genes that are located on the Y chromosome. Chromosomes are structures inside your cells that contain all of your genes. If you think of your DNA as a library, each chromosome is a book. Your genes are the chapters inside each book. Each chapter, or gene, contains specific instructions.

Humans have two sets of 23 chromosomes, for a total of 46. There are 22 pairs of autosomes plus one pair of sex chromosomes (the X and Y chromosomes). We inherit one set of chromosomes from our mother and one set from our father.

The image above shows normal male chromosomes, with one X and one Y chromosome. Women have two X chromosomes instead. The Y chromosome is passed from father to son.

What is a Y Deletion?

A Y chromosome deletion happens when a small part of the chromosome is missing. Y chromosome deletions can be large or small. Large deletions may be found by looking at a chromosome analysis like in the picture above.  However, most Y chromosome deletions are microdeletions. "Micro" means that the missing part is so small that it can't be detected through normal chromosome analysis. Instead, labs use advanced DNA testing techniques to decide whether there certain regions are there or not. The common Y chromosome deletions are called AZFa, AZFb, and AZFc.

The Y chromosome contains genes that are very important. They give instructions for an embryo to become male and to make sperm. If these genes are partially or completely deleted, they can cause a man to be infertile because of low or no sperm production.

Men usually learn that they have low or absent sperm by semen analysis. During a semen analysis, a specialist checks the number of sperm, how the sperm move, and how the sperm are shaped. "Severe oligospermia" describes very low numbers of sperm. "Azoospermia" describes a complete lack of sperm.

About 10% to 15% of men who have very low or no sperm have a Y chromosome microdeletion. Because these deletions cause infertility, they are usually not inherited from the father. Instead, they happen new and by chance. However, there are a few cases where a man with a Y microdeletion has fathered one or more sons who have the same deletion.

Next: Who Should Test for Y Microdeletions?

Why are you considering genetic testing?

I think I have infertility, but I haven't seen a doctor and/or had any testing yet.

I have low or absent sperm found on semen analysis during infertility testing.

I have infertility, but it isn't caused by low or absent sperm.

Genetic testing for Y microdeletions can be part of the evaluation for infertility, but it isn't the first step. This testing is only useful for men who have had a semen test already and know that they have low sperm count or no sperm found by that testing.

There are many different causes for infertility. If you and your partner are having trouble getting pregnant, you may consider seeing an infertility specialist. That doctor can review your history and order additional testing as indicated.

Genetic testing for Y microdeletions may be useful for you. About 10% to 15% of men with low or absent sperm not due to a physical block have a Y microdeletion. Testing may provide you with more information about your infertility and the reproductive options for you.

  • If you have a deletion, this would help to explain your infertility. Having information about your specific deletion can help guide your reproductive options. Finding an AZFc deletion is associated with better success for sperm retrieval. AZFa and AZFb or b/c deletions have a low success of sperm retrieval.

    Y microdeletions usually happen new in a man and are not inherited from a parent. However, there have been some cases where a man with a Y microdeletion fathered one or more sons with the same deletion. Testing would be available to your brothers if they are unsure of their fertility.

  • If you do not have a deletion, a genetic cause of infertility can't be ruled out. There may be other changes in the Y chromosome that haven't been found yet. There are other known genetic causes of infertility that are not tested for with this test.

If not already done, your doctor may also perform a chromosome analysis (karyotype). Some men with low or absent sperm have other chromosome changes that can be found with that testing.

Genetic testing for Y microdeletions can be part of the work up for infertility, but it isn't useful for everyone. This testing is useful for men who have had a semen test already and know that they have low sperm count or no sperm found by that testing. Since this is not the cause of your infertility, this testing is not likely to be helpful.

There are other genetic causes of infertility. If you have questions about whether any genetic testing may be right for you, you may wish to speak to a doctor or genetic counselor.