Genetics of Male Infertility
Y-Chromosome Microdeletions (AZFa/b/c), CFTR/CBAVD, Karyotype Abnormalities, and When to Test
Evidence grade 4 of 5, Strong. Read how the Atlas grades evidence.
The written rationale for this grade is still being prepared.
- FDA
- Diagnostic genetic testing (not a therapy); recommended by AUA/ASRM and EAA/EMQN guidelines for severe oligozoospermia and azoospermia
Reference only. Not medical advice.
What can go wrong
Genetic findings carry counseling consequences: AZFc and certain CFTR or chromosomal abnormalities can be transmitted to children conceived via ICSI - AZFc deletions pass to all sons (who will likely be infertile), and CBAVD requires testing the female partner for CFTR mutations to gauge cystic-fibrosis risk in offspring. Testing must be paired with genetic counseling, not delivered as a raw lab value. A normal panel does not exclude as-yet-uncharacterized genetic causes.
This is something to take to a clinician. The Atlas can tell you what is known about genetics of male infertility in general. It cannot tell you what is happening in your body, and the difference matters most for exactly the symptoms that bring people to this page.
In men with severe oligozoospermia or non-obstructive azoospermia, a defined trio of genetic tests carries real prognostic and counseling weight: karyotype, Y-chromosome microdeletion testing (AZFa, AZFb, AZFc), and CFTR mutation analysis. The findings change management - AZFa or complete AZFb deletions predict no retrievable sperm and spare a futile micro-TESE, AZFc still often yields sperm, and a CFTR-linked congenital absence of the vas is a treatable obstruction with hereditary cystic-fibrosis implications for offspring.
When the sperm count is near zero, the answer is often written in the DNA.
What people take it for
What it is taken for. Approval, where it exists, covers only some of these.
How it works
The Y chromosome's long arm carries Azoospermia Factor regions (AZFa, AZFb, AZFc) housing genes essential for spermatogenesis; deletions there impair or abolish sperm production with a region-specific prognosis. CFTR mutations (the cystic fibrosis gene) cause congenital bilateral absence of the vas deferens (CBAVD) - a developmental obstruction - so these men make sperm but cannot ejaculate them. Sex-chromosome and structural karyotype abnormalities (e.g., 47,XXY Klinefelter, translocations) impair the testis or carry transmission risk to embryos.
What people get wrong
Often saidA genetic cause means there is nothing you can do
ActuallyOften false. AZFc-deleted men frequently still have retrievable sperm for ICSI, and CBAVD men make normal sperm that can be retrieved surgically - the genetics guide, rather than end, the plan.
Often saidMicrodeletion type does not matter, just do the surgery
ActuallyIt matters greatly. AZFa and complete AZFb deletions predict essentially no sperm, so identifying them avoids a futile, costly micro-TESE.
Who profits, and who pushes back
Nobody is named here yet, because we have not done that work on this entry. Read that as unfinished. Somebody almost certainly sells this, and somebody almost certainly disputes it. Assume both until we have checked.
How we got here
The AZF concept dates to Tiepolo and Zuffardi's 1976 observation of Y-deletions in azoospermic men; molecular mapping in the 1990s (Vogt and colleagues) defined AZFa, AZFb, AZFc. CFTR's link to CBAVD emerged shortly after the 1989 cloning of the cystic-fibrosis gene. Together these turned severe male infertility from an opaque diagnosis into one with actionable, prognostic genetics.
- 1976Tiepolo & Zuffardi describe Y-chromosome deletions in azoospermia
- 1989CFTR gene cloned
- 1990sAZFa/b/c regions mapped; CFTR-CBAVD link established
- 2004/2014EAA/EMQN standardize Y-microdeletion testing and interpretation
What we do not know
- How many idiopathic azoospermia cases have undiscovered monogenic causes that next-generation sequencing will reveal?
- Should expanded gene panels or whole-exome sequencing become routine before micro-TESE?
- How best to counsel couples on transmitting infertility to ICSI-conceived sons (AZFc)?
At a glance
- When to test
- Severe oligozoospermia (<5 million/mL) or azoospermia
- The core trio
- Karyotype + Y-microdeletion (AZFa/b/c) + CFTR
- AZFa / complete AZFb
- Predict virtually no sperm on retrieval - avoid futile micro-TESE
- AZFc deletion
- Sperm often still retrievable; deletion passes to sons
What this entry does not yet cover
What follows is unfinished work on our side, not a finding about Genetics of Male Infertility. A short entry is not a safe entry.
- Cost and market. We have not documented what it sells for or who sells it.
- Supply chain. We have not mapped where it is made.
- Who uses it. We have not documented the user groups.
- What could change. No forward-looking summary yet.
- How it compares. We have not set it against the alternatives.
- Children and teenagers. We have not checked what is known about younger people.
Sources
The studies below are named and described, but not linked. You cannot open them from here and check our reading against them, which means this page is our summary of the literature rather than a document you can verify. Weigh it accordingly until the links exist.
The studies that matter
EAA/EMQN best-practice guidelines for Y-microdeletion testing2004, updated 2014 (Krausz et al.)
Standardized AZF testing and its prognostic interpretation - AZFa and complete AZFb deletions essentially preclude sperm retrieval
CFTR and CBAVD1990s onward (Chillon et al. 1995, NEJM and later)
Established that the great majority of men with congenital bilateral absence of the vas carry CFTR mutations, including the 5T allele, linking CBAVD to the cystic-fibrosis gene
Karyotype prevalence in azoospermiaMultiple cohorts
Chromosomal abnormalities (notably 47,XXY) are markedly enriched in azoospermic and severely oligozoospermic men versus the general population