Causes of Subfertility and Infertility – Male Factors

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Oligoasthenoteratozoospermia (OAT) is a condition that includes low sperm count (oligozoospermia), poor sperm movement (asthenozoospermia), and abnormal sperm shape (teratozoospermia). OAT is the most common cause of male subfertility.9, 15, 16 Several factors contribute to male subfertility and infertility.

Male Factors in Infertility

Click on sections below to reveal various factors.

Factors impacting sperm quality and quantity


  • Includes genes that may affect sperm production, movement, and transport
  • Chromosomal abnormalities such as Klinefelter syndrome


  • Includes disorders of the hypothalamus and pituitary gland, autoimmune conditions with anti-sperm antibodies, and hormone abnormalities such as hyperprolactinemia

Medical Condition:

  • Includes diabetes, varicocele, undescended testis, and injury
  • Infections such as chlamydia, gonorrhea, HIV, previous mumps, or tuberculosis
  • Medications including steroids, antidepressants, blood pressure medications, chemotherapy, and radiotherapy


  • Includes smoking, alcohol, and illicit drug use, as well as wearing tight underwear


  • Cause of infertility is unknown

Factors impacting sperm delivery

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  • Includes premature or retrograde ejaculation and conditions that affect the seminal fluid, such as:
    • Diminished production of prostatic fluid
    • Infection of the seminal vesicle
    • Cystic fibrosis


  • Includes injury to reproductive organs, blockage of the reproductive tract ducts (vas deferens, prostate, seminal vesicles), and scarring due to surgery, chemotherapy, or radiotherapy

Age and environmental factors

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  • In general, men above 35 years have half the chance of achieving fertilization than men 25 years old.
  • After the age of 55, the risk of chromosomal disorders increases.17, 18

Environmental Exposure:

  • Exposure to estrogenic industrial waste,19 and working in some industries such as the construction and plastic industries,20 have been attributed to reduced sperm density and increased incidence of testicular cancers. Environmental exposures have also been attributed to cryptorchidism (one or both of the testes fail to descend from the abdomen into the scrotum), and hypospadias (a congenital condition in which the opening of the urethra is on the underside of the penis)
  • A prospective study found higher sperm counts among organic farmers than electricians, printers, and metal workers, suggesting a possible role of environmental influences in reducing male fertility.21


  • Elevated temperature can reduce sperm quality. Occupations that increase the temperature of the testicles, including working near furnaces and long-distance driving, are associated with a higher risk of reduced sperm quality.22, 23
  • Artificial increase in scrotum or testicle temperature can reduce both sperm count and quality.

Note: References are listed at the end of the course.

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