Male Infertility Overview and Causes and Risk Factors

Infertility is the inability to conceive after at least one year of unprotected intercourse. Since most people are able to conceive within this time, physicians recommend that couples unable to do so be assessed for fertility problems.

In men, hormone disorders, illness, reproductive anatomy trauma and obstruction, and sexual dysfunction can temporarily or permanently affect sperm and prevent conception. Some disorders become more difficult to treat the longer they persist without treatment.

Sperm development (spermatogenesis) takes place in the ducts (seminiferous tubules) of the testes. Cell division produces mature sperm cells (spermatozoa) that contain one-half of a man's genetic code. Each spermatogenesis cycle consists of six stages and takes about 16 days to complete. Approximately five cycles are needed to produce one mature sperm. Energy-generating organelles (mitochondria) inside each sperm power its tail (flagellum) so that it can swim to the female egg once inside the vagina. Sperm development is ultimately controlled by the endocrine (hormonal) system that comprises the hypothalamic-pituitary-gonadal axis.

Because sperm development takes over 2 months, illness that was present during the first cycle may affect mature sperm, regardless of a man's health at the time of examination.

Incidence and Prevalence

According to the National Institutes of Health, male infertility is involved in approximately 40% of the 2.6 million infertile married couples in the United States. One-half of these men experience irreversible infertility and cannot father children, and a small number of these cases are caused by a treatable medical condition.

auses and Risk Factors

Common causes for male infertility are impaired sperm production, impaired sperm delivery, and testosterone deficiency(hypogonadism).

Infertility can result from a condition that is present at birth (congenital) or can develop later (acquired). Causes for infertility include the following:

• Chemotherapy 
  
• Defect or obstruction in the reproductive system (e.g., cryptorchidism, anorchism) 
  
• Disease (e.g., cystic fibrosis, sickle cell anemia, sexually transmitted disease [STD]) 
  
• Hormone dysfunction (caused by disorder in the hypothalamic-pituitary-gonadal axis) 
  
• Infection (e.g., prostatitis, epididymitis, orchitis) 
  
• Injury (e.g., testicular trauma)
  
• Medications (e.g., to treat high blood pressure, arthritis)
  
• Metabolic disorders such as hemochromatosis (affects how the body uses and stores iron)
  
• Retrograde ejaculation (i.e., condition in which semen flows backwards into the bladder during ejaculation) 
  
• Systemic disease (e.g., high fever, infection, kidney disease) 
  
• Testicular cancer 
  
• Varicocele
  

Retrograde ejaculation occurs when impairment of the muscles or nerves of the bladder neck prohibit it from closing during ejaculation. It may result from bladder surgery, a congenital defect in the urethra or bladder, or disease that affects the nervous system. Diminished or "dry" ejaculation and cloudy urine after ejaculation may be signs of this condition.

Testosterone Deficiency

Hypogonadism may be present at birth (congenital) or may develop later (acquired). Causes of the condition are classified according to their location along the hypothalamic-pituitary-gonadal axis:

• Primary, disruption in the testicles 
  
• Secondary, disruption in the pituitary gland 
  
• Tertiary, disruption in the hypothalamus 
  

The most common congenital cause is Klinefelter syndrome. This condition, which is caused by an extra X chromosome, results in infertility, sparse facial and body hair, abnormal breast enlargement (gynecomastia), and smaller than normal testes.

Congenital hormonal disorders such as leutenizing hormone-releasing hormone (LHRH) deficiency and gonadotropin-releasing hormone (GnRH) deficiency (e.g., Kallmann syndrome) also may cause testosterone deficiency.

Other congenital causes include absence of the testes (anorchism; may also be acquired) and failure of testicles to descend into scrotum (cryptorchidism).

Acquired causes for testosterone deficiency include the following:

• Chemotherapy 
  
• Damage to the pituitary gland, hypothalamus, or testes 
  
• Glandular malformation 
  
• Head trauma affecting the hypothalamus 
  
• Infection (e.g., meningitis, syphilis, mumps) 
  
• Isolated LH deficiency (e.g., fertile eunuch syndrome) 
  
• Radiation 
  
• Testicular trauma 
  
• Tumors of the pituitary gland, hypothalamus, or testicles