The causes of male infertility are mainly due to poor sperm counts, poor sperm motility & failure of sperm delivery.

A number of things can cause impaired sperm count or mobility, or impaired ability to fertilize the egg. The most common causes of male infertility include abnormal sperm production or function, impaired delivery of sperm, general health and lifestyle issues, and overexposure to certain environmental elements.

Impaired production or function of sperm. Most cases of male infertility are due to problems with the sperm, such as:

Impaired shape and movement of sperm. Sperm must be properly shaped and able to move rapidly and accurately toward the egg for fertilization to occur. If the shape and structure (morphology) of the sperm are abnormal or the movement (motility) is impaired, sperm may not be able to reach or penetrate the egg.

Low sperm concentration. A normal sperm concentration is greater than or equal to 20 million sperm per milliliter of semen. A count of 10 million or fewer sperm per milliliter of semen indicates low sperm concentration (subfertility). Complete failure of the testicles to produce sperm is rare.

Varicocele. A varicocele is a varicose vein in the scrotum that may prevent normal cooling of the testicle, leading to reduced sperm count and motility. This is the most common cause of an abnormal semen analysis.

Undescended testicle. Undescended testicle occurs when one or both testicles fail to descend from the abdomen into the scrotum during fetal development. Because the testicles are exposed to the higher internal body temperature, compared with the temperature in the scrotum, sperm production may be affected.

Testosterone deficiency (male hypogonadism). Infertility can result from disorders of the testicles themselves or from an abnormality affecting the hypothalamus or pituitary gland in the brain that produces the hormones that control the testicles.

Infections. Infection may temporarily affect sperm motility. Repeated bouts of sexually transmitted diseases (STDs), such as chlamydia and gonorrhea, are most often associated with male infertility. These infections can cause scarring and block sperm passage. If mumps, a viral infection usually affecting young children, occurs after puberty, inflammation of the testicles can impair sperm production. Inflammation of the prostate (prostatitis), urethra or epididymis also may alter sperm motility. In many instances, no cause for reduced sperm production is found. Often when reduced counts are noted, intrauterine insemination is indicated.

Impaired delivery of sperm. Problems with the delivery of sperm from the penis into the vagina can result in infertility. These may include:

Sexual issues. Often treatable, problems with sexual intercourse or technique may affect fertility. Difficulties with erection of the penis (erectile dysfunction), premature ejaculation, painful intercourse (dyspareunia), or psychological or relationship problems can contribute to infertility. Use of lubricants such as oils or petroleum jelly can be toxic to sperm and impair fertility.

Retrograde ejaculation. This occurs when semen enters the bladder during orgasm rather than emerging out through the penis. Various conditions can cause retrograde ejaculation, including diabetes, bladder, prostate or urethral surgery, and the use of certain medications.

Blockage of epididymis or ejaculatory ducts. Some men are born with blockage of the part of the testicle that contains sperm (epididymis) or ejaculatory ducts. Some men lack the tube that carries sperm (vas deferens) from the testicle out to the opening in the penis.

No semen (ejaculate). The absence of ejaculate may occur in men with spinal cord injuries or diseases. This fluid carries the sperm from the penis into the vagina.

Misplaced urinary opening (hypospadias). A birth defect can cause the urinary (urethral) opening to be abnormally located on the underside of the penis. If not surgically corrected, this condition can prevent sperm from reaching the woman’s cervix.

Anti-sperm antibodies. Antibodies that target sperm and weaken or disable them usually occur after surgical blockage of part of the vas deferens for male sterilization (vasectomy). Presence of these antibodies may complicate the reversal of a vasectomy.

Cystic fibrosis. Men with cystic fibrosis often have a missing or obstructed vas deferens.
General health and lifestyle.

A man’s general health and lifestyle may affect fertility. Some common causes of infertility related to health and lifestyle include:

Emotional stress. Stress may interfere with certain hormones needed to produce sperm. Your sperm count may be affected if you experience excessive or prolonged emotional stress. A problem with fertility itself can sometimes become long term and discouraging, producing more stress.

Malnutrition. Deficiencies in nutrients such as vitamin C, selenium, zinc and folate may contribute to infertility.

Obesity. Increased body mass may be associated with fertility problems in men.
Cancer and its treatment. Both radiation and chemotherapy treatment for cancer can impair sperm production, sometimes severely. The closer radiation treatment is to the testicles, the higher the risk of infertility. Removal of one or both testicles due to cancer also may affect male fertility.

Alcohol and drugs. Alcohol or drug dependency can be associated with poor health and reduced fertility. The use of certain drugs also can contribute to infertility. Anabolic steroids, for example, which are taken to stimulate muscle strength and growth, can cause the testicles to shrink and sperm production to decrease.

Other medical conditions. A severe injury or major surgery can affect male fertility. Certain diseases or conditions, such as diabetes, thyroid disease, Cushing’s syndrome, or anemia may be associated with infertility.

Age. Men older than age 40 may be less fertile than younger men.

Environmental exposure. Overexposure to certain environmental elements such as heat, toxins and chemicals can reduce sperm count either directly by affecting testicular function or indirectly by altering the male hormonal system. Specific causes include:

• Pesticides and other chemicals.
• Herbicides and insecticides may cause female hormone-like effects in the male body and may be associated with reduced sperm production and testicular cancer.
• Lead exposure may also cause infertility

Overheating the testicles. Frequent use of saunas or hot tubs can elevate your core body temperature. This may impair your sperm production and lower your sperm count.
Substance abuse. Use of cocaine or marijuana may temporarily reduce the number and quality of your sperm.

Tobacco smoking. Men who smoke may have a lower sperm count than do those who don’t smoke.