Infertility affects 15% of couples attempting pregnancy in the United States. Roughly speaking, about half of these couples will have a male factor involved, and a male factor will be the sole cause of infertility in about 25% of cases. Thus, all men should have at least a basic evaluation by a urologist early in the course of the female’s evaluation to avoid expensive and unnecessary female treatments.
Infertility is defined as the inability to achieve pregnancy after 1 year of unprotected intercourse. Many couples seek medical attention prior to waiting a year, especially if the female partner is over 35 years old. Most couples who seek medical assistance for fertility do not require high technology, expensive treatments
The male reproductive system consists of internal and external sex organs (Fig. 1A) that are under sensitive hormonal control from structures in the brain such as the pituitary gland and hypothalamus (Fig 1B). Normally, the hypothalamus secretes molecules that then stimulate the pituitary gland to produce hormones that are necessary for testis function. Testis function can be most simply divided into endocrine and exocrine function. The endocrine function of the testis includes production of testosterone, a critical steroid hormone that helps form and maintain the function of the male sex organs, stimulates sperm production, and regulates secretion of pituitary hormones to prevent their overproduction. The exocrine function of the testis consists of a remarkably high output of sperm, the cells necessary to carry the male’s genetic material to the female egg to produce an embryo. From start to finish, sperm take roughly 74 days to form. From the testis, sperm are secreted into the epididymis, a highly convoluted single tubular organ residing behind each testicle. It is in the epididymis that sperm gain their ability to swim as well as other important maturational qualities.
Normally, mature and some immature sperm are expelled from the urethra during ejaculation. Orgasm is a complex neurological event in which sperm are deposited from the paired vas deferens tubes (emission) where they join important secretions from other glands situated behind the urinary bladder (prostate gland and seminal vesicles) before being forcefully emitted from the penis (ejaculation). The sperm and seminal fluids normally enter the urethra within the prostate gland and are prevented from flowing into the bladder (retrograde ejaculation) by tight closure of the bladder neck at the time of orgasm.
While there is no one strict definition for a “normal” semen analysis, the World Health Organization (WHO) has determined minimal standards of what can be considered adequate semen quality for conception to occur. It is important to realize that these represent minimum standards and not necessarily “normal” values found in fertile men.
WHO Criteria for Minimum Semen Standards
|Sperm concentration||> 15 million/cc|
|Total sperm count||> 22.5 million/ejaculate|
|Morphology||> 4% normal forms (strict criteria)|
|Vitality||> 50% alive (vital staining)|
|(Adapted from WHO laboratory manual for the examination of human semen and sperm-cervical mucus interaction. Fourth edition, 2010.|
What Can Go Wrong
Male factor abnormalities are diverse, but generally include hormonal problems (pre- testicular), intrinsic testicular problems (testicular), and problems with ducts leading from the testes (post-testicular).
Sperm production is dependent on the careful balance of pituitary gland and testicular hormones. The main pituitary hormones involved in reproduction are follicle stimulating hormone (FSH) and leutinizing hormone (LH). These are the same hormones that are often tested in the female partner.
Prolactin (PRL) is another pituitary hormone that, if elevated, drastically inhibits sperm production and function. A complete hormonal evaluation should be done in all men presenting with infertility. This is done with a simple blood test. While hormone problems account for only 10% of male fertility problems, most are easily treatable.
Intrinsic testicular problems
Testis problems result in a decline in sperm production and/or function. The causes of these problems are very diverse and require a complete evaluation done by a urologist specializing in fertility. Many of these can be detected on a simple physical examination.
A very common cause of testicular problems is a varicocele, or set of dilated veins surrounding the testes. These are simply an abundance of the normally found veins in the spermatic cord, or cable leading through the groin area to the testis on each side. These veins are no different the varicose veins seen in the legs of some people and are caused by gravity’s effect (see section on evaluation and treatment).
Problems with the ducts leading from the testicles
In some men, impaired fertility is caused by a failure of normally produced sperm in the testes to get to the outside world. The following represents the normal course of sperm once it is produced in the testis:
Testis –> epididymis –> vas deferens –> ejaculatory ducts –> urethra
The epididymis is a gland sitting on the back of each testis that consists of a single, fine tube where sperm mature and gain their ability to swim (become motile). The epididymis can become obstructed from acquired or congenital problems. Acquired causes of epididymal obstruction include mumps infection, epididymitis, and trauma. Occasionally, the epididymis can be obstructed at birth for unknown reasons (congenital).
The vas deferens are paired tubes that carry sperm from the epididymis to the ejaculatory ducts of the prostate gland. They are the tubes that are divided during a vasectomy. Acquired causes of vasal blockage are rare. The most common is vasal injury at the time of inguinal hernia repair, especially during childhood hernia repair. Congenital causes of vasal blockages are also rare. The most common of these is a complete absence of the vas tubes on each side called congenital bilateral absence of the vas deferens (CBAVD). This produces a complete absence of sperm in the ejaculation and can only be diagnosed by a careful physical examination. CBAVD is also linked to being a carrier for the lung disease cystic fibrosis. Careful genetic testing is necessary in all patients with this condition.
The ejaculatory ducts are paired ducts that traverse the prostate gland to carry sperm from the terminal portion of the vas tubes to the urethra. In some cases, these ducts can be blocked. This usually leads to low ejaculate volume and poor sperm counts. The cause is usually congenital, consisting of a benign cyst in the prostate that blocks flow through these very fine ducts. Treatment is curative, but requires the correct diagnosis.
Once the sperm is deposited in the urethral tube, expulsion of the semen through the penis requires a complex set of neurological events to occur in which the bladder opening is closed off so that semen cannot travel backwards into the bladder. This condition is called retrograde ejaculation. It is not dangerous, but inhibits fertility profoundly. Causes include medications, diabetes, previous bladder surgeries and unknown causes. Patients with this condition are almost universally fertile and high pregnancy rates can be obtained with treatment.