Azoospermia, found in 1% of all men and 15% of infertile men, involves an absence of sperm in ejaculation. It may result from various issues, including blockages, hormonal imbalances, ejaculation problems, or testicular abnormalities. Some causes are treatable, while others may involve retrieving live sperm for assisted reproductive techniques like IVF.
Types of Azoospermia
Azoospermia comes in three primary forms. The first one is pretesticular azoospermia, which arises when the testicles are normal, but the body fails to stimulate sperm production, often due to low hormone levels or post-chemotherapy effects.
Secondly, testicular azoospermia results from damage to the testicles, which can be caused by various factors, including infections in the reproductive tract, childhood illnesses, injuries, cancer, radiation treatments, or genetic conditions.
The third type, post-testicular azoospermia, occurs when the testicles can produce sperm as usual, but an obstruction prevents their release.
This obstruction might be in the tubes carrying sperm to the penis (obstructive azoospermia), result from a vasectomy, or stem from retrograde ejaculation, where semen enters the bladder rather than being expelled during orgasm. Notably, approximately 40% of men with azoospermia have the post-testicular form.
Azoospermia may be detected through medical tests in which diagnosis involves examining semen samples under a high-powered microscope. If no sperm are detected on two separate occasions, azoospermia is confirmed.
Subsequently, medical professionals conduct a series of tests, including a physical examination, medical history review, and hormone level assessments. Imaging tests such as ultrasounds may be used to identify potential obstructions. If no physical blockage is found, genetic tests are employed to explore genetic factors linked to azoospermia.
In-Depth Examination of Sperm Formation
Ordinarily, the testicles generate sperm, which combines with fluids to create semen, the fluid released during ejaculation. A recent study, published in Science Advances, investigates the critical protein structure required for sperm and egg production and found that changing a specific point in this structure in mice caused infertility, shedding light on male infertility in humans due to similar issues with meiosis.
It is the process that leads to sperm and egg formation and involves the creation of the synaptonemal complex, a protein structure that acts like a bridge, ensuring the correct separation of chromosomes into reproductive cells. This complex has been of great interest to understand the origins of infertility, particularly in cases involving defects in meiosis.
While previous research had explored various components of the synaptonemal complex, the study delved into a specific protein that forms the lattice-like bridge in this structure. This protein is shared across various species, including humans and mice, suggesting its importance in assembly.
Using gene editing techniques, the researchers introduced mutations in this protein in mice, enabling them to test the function of different regions within the protein. They confirmed that just a single mutation in the protein was responsible for infertility in mice.
The study's findings indicate the potential for similar infertility mechanisms in humans, given the conservation of this protein structure across species. This research showcases how the Stowers Institute's resources and adaptability allowed scientists to investigate and understand essential biological processes. This knowledge could contribute to significant advancements in infertility research and treatment.
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