Male infertility, a condition affecting a man’s ability to initiate a pregnancy, is a significant factor in reproductive challenges. Male factors contribute to roughly half of all infertility cases experienced by couples seeking fertility treatment. Infertility, defined as the inability to conceive after at least one year of regular unprotected intercourse, affects approximately 15% of couples globally.
Hormonal and Systemic Factors
Male infertility can stem from hormonal imbalances and systemic conditions that impact sperm production and function. Hormones like testosterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) are crucial for healthy sperm development. Imbalances, such as low testosterone (hypogonadism), can directly lead to decreased sperm production. Elevated levels of prolactin can also suppress testosterone and impair testicular function, further reducing sperm count.
Systemic illnesses also play a role by disrupting the hormonal environment or affecting overall reproductive health. Chronic conditions like kidney disease, liver disease, and diabetes can negatively influence sperm parameters. For instance, men with advanced chronic kidney disease often experience low sperm count or absence of sperm due to impaired hormonal homeostasis and testicular function. Obesity can similarly impact fertility by altering hormone levels, including increasing estrogen and lowering free testosterone, which interferes with sperm production. Certain medications, including some chemotherapies, narcotics, and anabolic steroids, can also disrupt hormonal regulation necessary for healthy sperm development, leading to reduced sperm count.
Sperm Production Impairments
Issues directly affecting the testes, where sperm are produced, represent a common category of male infertility. Varicocele, an enlargement of veins within the scrotum, is a frequent cause of sperm production problems. Varicoceles can lead to increased scrotal temperature, which negatively impacts sperm quantity and quality. This can result in low sperm count (oligospermia), poor sperm movement (asthenozoospermia), or abnormally shaped sperm (teratozoospermia).
Genetic conditions can also severely impair sperm production. Klinefelter syndrome, a chromosomal disorder, is a common genetic cause of male infertility, often leading to azoospermia, the complete absence of sperm. Y-chromosome microdeletions, particularly in the Azoospermia Factor (AZF) regions, are another significant genetic cause, resulting in reduced or absent sperm production. Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene can also cause male infertility by affecting sperm transport.
Other factors directly impacting testicular function include undescended testes (cryptorchidism), where one or both testes fail to descend into the scrotum. The higher temperature within the body’s abdominal cavity can impair testicular development and sperm production, leading to infertility, especially in bilateral cases. Infections, such as mumps orchitis or epididymitis, can cause testicular damage and lead to reduced sperm production or blockages. Physical trauma to the testes, as well as exposure to environmental toxins or radiation, can directly harm sperm-producing cells, resulting in impaired sperm development or absence.
Sperm Transport and Delivery Issues
Even with healthy sperm production, male infertility can arise from problems with sperm transport and delivery. These issues prevent sperm from reaching the female reproductive tract successfully. Blockages within the reproductive tract are a common cause, such as obstructions in the vas deferens or epididymis. These obstructions can be congenital, like bilateral absence of the vas deferens, or acquired due to prior infections or surgeries that cause scarring.
Ejaculatory disorders also fall into this category. Retrograde ejaculation occurs when semen travels backward into the bladder instead of exiting through the penis during orgasm. This happens because the muscles at the bladder neck do not close properly, leading to little or no semen being expelled, making natural conception difficult. Anejaculation, the complete absence of ejaculation, can result from nerve damage, certain medical conditions like diabetes, or psychological factors. If sperm are produced, they still cannot be delivered for fertilization.
Sexual function issues further contribute to delivery problems. Erectile dysfunction, the inability to achieve or maintain an erection firm enough for intercourse, directly prevents sperm deposition. Premature ejaculation, while not directly affecting sperm quality, can hinder successful sperm delivery if ejaculation occurs before vaginal penetration or too early in intercourse. These functional problems create a physical barrier or timing issue that impedes the journey of sperm to the egg.
Unexplained Infertility
In a notable percentage of cases, despite comprehensive medical evaluation, no specific cause for male infertility can be identified. This is termed unexplained infertility. While frustrating for couples, this diagnosis means current diagnostic methods have not yet pinpointed a cause. Approximately 10% of infertility cases are classified as unexplained, highlighting the limitations of current understanding and diagnostic tools.