Causes of Male Infertility

How Male Infertility Occurs

Sperm are manufactured in the testicles and stored inside the epididymis, a gland that lies on top of each testis. Semen nourishes the sperm until ejaculation occurs. A half-teaspoon of semen contains around 150 million sperm. Male infertility occurs when this process is altered by medical, environmental, or hormonal causes. Common medical causes of male infertility include varicocele, undescended testicles, infections of the male reproductive tract, chemotherapy, medications, and genetic abnormalities. Hormonal causes of male infertility include hypothyroidism, hyperprolactinemia, congenital adrenal hyperplasia, and hypogonadotrophic hypopituitarism. Hormonal problems include the brain failing to release gonadotrophin-releasing hormone (GnRH), a substance necessary for testosterone synthesis and sperm production or the pituitary failing to produce luteinizing hormone (LH) and follicle stimulating hormone (FSH), which are necessary to stimulate the testes to produce sperm. Common environmental causes of male infertility include heat, exposure to certain heavy metals, radiation, and industrial chemicals.

Medical Causes

Numerous problems with male infertility occur from health conditions and medical treatments. These include:

  • Varicocele. A varicocele is a swelling of veins that should drain the testicle, and this condition is the most common cause of male infertility. A varicocele prevents cooling of the testicle, therefore reducing sperm count and motility. With this condition, the spermatic veins become damaged, leading to an abnormal blow of blood from the abdomen to the scrotum. This creates a hostile environment for sperm development, altering sperm count and morphology.
  • Undescended testicles. During fetal development, the testicles of some males do not descend from the abdomen into the scrotal sac. This can affect one or both of the testes. Undescended testicles is a common cause of decreased fertility.
  • Infections of the male reproductive tract. Some infections interfere with sperm health, the production of sperm, or from scarring that blocks the sperm from exiting the penis. Sexually transmitted infections (STIs) include gonorrhea and chlamydia. Other infections of the male reproductive tract and testes include prostatitis, urethritis, orchitis, and epididymitis.
  • Anti-Sperm antibodies. Antibodies that attack sperm are called anti-sperm antibodies. These are immune system cells that identify sperm as harmful invaders and try to eliminate them.
  • Ejaculation issues. Retrograde ejaculation occurs when semen goes into the bladder during orgasm instead of passing out the tip of the penis. Conditions that cause this ejaculation issue include spinal injuries, diabetes, medications, and surgery or the male reproductive tract.
  • Tumors and cancers. Certain cancers and nonmalignant tumors can affect the male reproductive organs or the glands that release necessary sex hormones, such as the pituitary gland.
  • Sperm duct defects. The tubes that carry sperm are called sperm ducts. These structures can be damaged from injury or illness. When there is a blockage in the area of the testicle that stores the sperm or interference with the tubes that transport sperm, infertility occurs. Men with cystic fibrosis and other inherited disorders are often born without sperm ducts. Around seven percent of infertile men cannot transport sperm from the testicles out of the penis. Scarring from STIs or tuberculosis also can block the tubes and epididymis.
  • Testicular torsion. A common problem with fertility is testicular torsion. This is caused by a supportive tissue abnormality, which causes the testes to twist inside the scrotum and swell. With this condition, the blood vessels that supply the testes are blocked and serious infertility occurs when surgery is not done.
  • Infections and diseases. Sexually transmitted infections and other diseases can cause testicular atrophy or block the epididymis. This leads to a low sperm count and decreased sperm motility. Common infections and diseases include gonorrhea, chlamydia, syphilis, mumps, tuberculosis, brucellosis, typhoid, smallpox, and influenza.
  • Chromosomal defects. There are several inherited disorders that cause male infertility. Klinefelter's syndrome is a condition where the male is born with two X chromosomes and one Y chromosome instead of one of each X and Y. This causes abnormal development of the male reproductive organs. Other genetic conditions that can lead to infertility include Young's syndrome, Kartagener syndrome, cystic fibrosis, and Kallmann's syndrome.
  • Celiac disease. Celiac disease is a digestive disorder caused by increased sensitivity to gluten. This condition is a rare cause of male infertility.
  • Medications. Many drugs and medicines affect fertility, including testosterone replacement therapy, long-term anabolic steroid use, chemotherapy agents, certain antifungal drugs, and some antiulcer medications. These agents impair sperm production or alter fertility by affecting the pituitary-gonadal axis.
  • Problems With Sexual Intercourse. Erectile dysfunction can interfere with keeping and/or maintaining an erection for sexual intercourse. Other problems that affect male fertility include painful intercourse, premature ejaculation, and anatomical abnormalities, such as hypospadias.

Hormonal Causes

A small percentage of fertility problems are caused by hormonal conditions or altered levels of hormones. The hypothalamus-pituitary-endocrine (HPE) system regulates the chain of hormonal events that allows the testes to produce and transport sperm. When there is a problem with the HPE system, infertility could occur. Common hormonal causes of male infertility are:

  • Hyperprolactinemia. Elevated prolactin (a hormone needed for sperm production) reduces libido and can lead to impotence. This condition is treated with Parlodel (bromocriptine).
  • Hypothyroidism. Low levels of thyroid hormone can cause poor semen quality, disturb libido, and affect testicular function. This condition is found in one percent of infertile men.
  • Congenital Adrenal Hyperplasia. When there are increased levels of adrenal androgens, it causes low sperm count, decreased motility, and immature sperm cells. This condition is treated with cortisone replacement therapy.
  • Hypogonadotrophic Hypopituitarism. This condition involves a low output of LH and FSH, two hormones needed for sperm production. Without these hormones, the Leydig cells that produce testosterone deteriorate and the seminiferous tubules become dysfunctional. This is treated with the drug Serophene.

Environmental Causes

Overexposure to certain elements in the environment can reduce or alter sperm function and production. Specific environmental causes include:

  • Industrial chemicals. These include benzenes, xylene, toluene, pesticides, herbicides, organic solvents, and painting materials.
  • Heavy metals. These include lead and mercury.
  • Radiation. Overexposure to X-Rays or radiation therapy can reduce sperm production.
  • Heat. Overheating the testicles can lower the sperm count. This occurs from wearing tight clothing, frequent use of hot tubs, or working on a laptop for an extended period of time.

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