There are many possible causes of male infertility. Your doctor should perform a thorough physical examination and should be interested in any factor, including possible structural and other defects in the reproductive system, hormonal deficiencies, illness or even trauma that might be impairing your fertility. Their investigation will center on a number of different factors, the most common of which are:
Sperm Production or Delivery
Sperm disorders: Problems with the production and development of sperm are the most common problems of male infertility. Sperm may be underdeveloped, abnormally shaped, carrying damaged genetic material, or unable to move properly. Alternatively, normal sperm may be produced in abnormally low numbers (oligospermia) or seemingly not at all (azoospermia).
Varicoceles: Varicoceles are dilated scrotal veins that are present in about 15 percent of all men but are more common in infertile men – about 40 percent. They impair sperm development by preventing proper drainage of blood from the testicles back into the abdomen. Varicoceles may be easily discovered on physical examination since the veins feel distinctively like a bag of worms. They may also be enlarged and twisted enough to be visible in the scrotum. Varicoceles are the most common correctable and treatable cause of male infertility.
Retrograde ejaculation: Retrograde ejaculation occurs when semen is pushed backwards into the bladder instead of out the penis. This is caused by the failure of nerves and muscles in the bladder neck to close during orgasm. It is one of several difficulties couples may have delivering sperm to the vagina during intercourse. Previous surgery, medications or diseases affecting the nervous system can cause retrograde ejaculation. Signs of this condition may include cloudy urine after ejaculation and diminished or "dry" ejaculation with orgasm.
Immunologic infertility: Triggered by a man's immunologic response to his own sperm, the production of antisperm antibodies results from injury, surgery or infection of the reproductive tract. In attacking the sperm, antibodies prevent normal movement and function of the sperm. Although researchers do not yet understand just exactly how antibodies damage fertility, they know that these antibodies can make it more difficult for sperm to swim to the uterus and penetrate eggs. Immunologic infertility can be found by checking a semen analysis for antisperm antibodies.
Obstruction: Blocking sperm from its normal passage, obstructions can be caused by a number of factors, such as repeated infections, prior surgery (including vasectomy), and inflammation or development problems. Any portion of the male reproductive tract, such as the vas deferens, the epididymis, or the ejaculatory duct inside the prostate can be obstructed, preventing normal transport of sperm from the testicles to the urethra, where it leaves the body during ejaculation.
Physical, Hormonal or Genetic
Erectile Dysfunction : The inability to achieve and/or maintain an erection may impede intercourse, limiting the chances for conception.
Hypogonadism: Hypogonadism, also known as low testosterone, occurs when the testes produce little or no hormones.
Hormones: Some hormones produced by the pituitary gland are responsible for stimulating the testicles to make sperm. When levels of these hormones are severely low, poor sperm development can result.
Genetics: Genetics play a central role in fertility, particularly since sperm carry half of the DNA mix to the partner's egg. Abnormalities in chromosomal numbers and structure as well as deletions on the important Y chromosome present in normal males can also impact fertility.
Spermatocele: A spermatocele, also known as a spermatic or epididymal cyst, is typically a painless, noncancerous (benign) fluid filled cyst that is a sack of fluid arising from the epididymis. It usually sits near the top and/or behind the testicle, but appears separate from the testis. Spermatoceles can block sperm from exiting the epididymis. Likewise, surgery to remove spermatoceles may cause scarring of the epididymis that can prevent sperm from entering the semen.
Testicular torsion: Testicular torsion, or twisting of the testicle resulting in a strangulation of the blood supply, occurs in men whose tissue surrounding the testicle is not well attached to the scrotum. It is important to emphasize that testicular torsion is an emergency. The testicle will die (infarct) and diminish in size (atrophy) if the blood supply is not restored within approximately six hours. Restoration of the blood supply typically requires surgery to untwist the spermatic cord (de-torsion).
Undescended testis: An undescended testicle occurs when a testicle fails to reach the normal position in the scrotum. It may be found high up in the scrotum, in the groin, or even inside the abdomen. While the exact cause of infertility in men with undescended testicles is unknown, many men with undescended testicles have low sperm counts and/or poor quality sperm.
Epididymitis: Epididymitis is swelling (inflammation) of the epididymis, the tube that connects the testicle with the vas deferens. Epididymitis may be due to infections as well as non-infectious causes.
Orchitis: Orchitis is swelling (inflammation) of the testicle. Often times, the combination of epididymo-orchitis is present.
Hydrocele: A hydrocele is a fluid-filled sack in the scrotum that surrounds the testicle. It may occur on one or both testicles.
Inguinal hernias: A hernia is a sac formed by the lining of the abdominal cavity (peritoneum). The sac comes through a hole or weak area in the fascia, the strong layer of the abdominal wall that surrounds the abdominal muscles.
Lifestyle & Environment
Age: Men older than age 40 may be less fertile.
General Lifestyle: General health and lifestyle issues, such as poor nutrition, obesity, or use of alcohol, tobacco and drugs may contribute to fertility issues in men.
Medication: Certain medications can affect sperm production and function, as well as erectile and ejaculatory function. Such medications are usually prescribed to treat conditions like arthritis, depression, digestive problems, infections, high blood pressure and even cancer.