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What are the most common causes of male infertility?

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Varicoceles are dilated veins in the scrotum, (just as an individual may have varicose veins in their legs.) These veins are dilated because the blood does not drain properly from them. These dilated veins allow extra blood to pool in the scrotum, which has a negative effect on the sperm production. This condition is the most common reversible cause of male factor infertility and may be corrected by minor outpatient surgery.

Most experts do this microscopically to preserve the arterial supply and lymphatics. A sub-inguinal incision (about 1 inch above the penis and 1 inch from the midline) is usually used, as this avoids incising the abdominal muscles and creates less post-operative pain.

Abnormalities in the seminal fluid

If the seminal fluid is very thick it may be difficult for the sperm to move through it and into the woman’s reproductive tract. Often the semen can be processed to separate the moving sperm from the surrounding debris, dead sperm and seminal fluid. The processed sperm is usually placed directly inside the uterus with a small tube (catheter). This is called intrauterine insemination (IUI).

Problems with the ductal system

Sperm carrying ducts may be missing or blocked.

A patient may have bilateral (both sides) congenital (from birth) absence of the vas deferens.

He may have obstructions either at the level of the epididymis (the delicate tubular structure draining the testes) or higher up in the more muscular vas deferens. He may have become mechanically blocked during hernia or hydrocele repairs. He may have become blocked by scar tissue as a response to an infection.

Sperm are stored in sacs called the seminal vesicles and are then deposited in the urethra which is the tube through which men urinate and ejaculate. The sperm must pass through the ejaculatory ducts to get from the seminal vesicles to the urethra. If these are blocked on both sides no sperm will come through.

In some situations the ducts may be repaired or unblocked, to allow them to flow throught the man's reproductive tract. If this is not possible, the sperm may be harvested, but because they are obtained in lower numbers, they must then be used in conjunction with advanced reproductive techniques to attempt a pregnancy.

Immunologic Infertility

Men can develop an immunologic response, (antibodies) to their own sperm. The causes for this may include testicular trauma, testicular infection, large varicoceles or testicular surgery. Sometimes there are unexplained reasons why this occurs.

These antibodies have a negative effect on fertility although the exact reason why this is the case is unclear. Most likely these antibodies act negatively at several points along the pathway to fertilization. They make it more difficult for the sperm to penetrate the partner’s cervical mucous and make its way into the uterus. They make it more difficult for the sperm to bind with the zonapellucida (the external membrane or shell of the egg). Also, the antibodies make it more difficult for the sperm to fuse with the membrane of the oocytes (eggs) themselves.

The treatment for anti-sperm antibodies is somewhat controversial. Men may be treated with corticosteroids. However, this can lead to significant morbidity in the man. The most significant is aseptic necrosis of the hip (noninfectious destruction of the joint) requiring hip replacement.

Most of the time, the first level of intervention includes intra-uterine inseminations. If the couple is planning invitro fertilization, (IVF) the presence of anti-sperm antibodies is usually an indication to inject the sperm directly into the egg (ICSI) instead of conventional IVF.

Difficulties with erections and ejaculation

About 5% of couples with infertility have factors relating to intercourse. This includes the inability to obtain or maintain an erection, premature ejaculation, lack of ejaculation, retrograde (backwards) ejaculation, lack of appropriate timing of intercourse and excessive masturbation. Interestingly, the most common problem is infrequency of intercourse. Many men will have difficulty with erections under the pressure at trying to achieve a conception. These couples can easily learn the technique of self inseminations.Studies have shown that 5 out of 6 previously fertile couples having intercourse four times per week will conceive over six months, while only 1 out of 6 with intercourse once per week will conceive during the same period.

Testicular Failure

This generally refers to the inability of the sperm producing part of the testicle (the seminiferous epithelium) to make adequate numbers of mature sperm. This failure may occur at any stage in sperm production for a number of reasons. The testicle may completely lack the cells that divide to become sperm (“Sertoli Cell-Only syndrome”). There may be an inability of the sperm to complete their development (" maturation arrest"). Sperm may be made in such low numbers that few if any successsfully travel through the ducts and into the ejaculated fluid (hypospermatogeneses). This situation may be caused by genetic abnormalities, hormonal factors, or varicoceles.

Even in the case where the testes are only producing low numbers of sperm, the sperm may be harvested and used in conjunction with advanced reproductive techniques to attempt a pregnancy.


Cryptorchidism may be a cause of testicular failure. When a baby boy is born without the testes having fully descended into the scrotum the condition is known as cryptorchidism.

Since the testes are very sensitive to temperature, if they do not descend into the scrotum prior to adolescence, then they will stop producing sperm altogether. In fact, they have a higher rate of malignancy. The current recommendation is that at approximately one year of life, if they have not yet descended by themselves, they be brought down surgically.

Cryptorchidism is often associated with male factor infertility. 81% men who have a single testis that is cryptorchid have normal fertility. However, approximately only 50% of men who have bilateral cryptorchidism have normal fertility. This may be due both to something inherent in the testes, to the surgery, or to the damage done by not having brought the testes down in time.


There are a number of fairly common drugs, which may have a negative effect on sperm production and or function. They include:

  • Ketoconazole (an anti-fungal)
  • Sulfasalazine (for inflammatory bowel disease)
  • Spironolactone (an anti-hypertensive)
  • Calcium Channel Blockers (anti- hypertensives)
  • Allopurinol, Colchicine (for gout)
  • Antibiotics: Nitrofuran, Erythromycin, Gentamicin
  • Methotrexate (cancer, psoriasis, arthritis)
  • Cimetidine (for ulcers or reflux)

The following list of drugs can cause ejactulatory dysfunction:

  • Antipsychotics: Chlorpromazine, Haloperidol, Thioridazine
  • Antidepressants: Amitriptyline, Imipramine, Fluoxetine (Prozac), Paroxetine (Paxil), Sertraline (Zoloft)
  • Antihypertensives: Guanethidine, Prazosin, Phenoxibenzamine, Phentolamine, Reserpine, Thazides

Hormonal Abnormalities

The testicles need pituitary hormones to be stimulated to make sperm. If these are absent or severely decreased the testes will not maximally produce sperm. Importantly, men who take androgens (steroids) either by mouth or injection for body building shut down the production of hormones for sperm production.

A hormonal profile must be performed on all men with male factor infertility. This will help rule out serious medical conditions, give more information on the sperm-producing ability of the testes, and may reveal situations where hormonal treatment is indicated.


Men may have infections of their reproductive tract. These may include infections of the prostate (prostatitis), of the epididymis (epididymitis), or of the testis (orchitis).

Post-pubertal viral infections of the testes may cause significant damage (atrophy) of the testes and may cause absolute and irreversible infertility. Bacterial infections or sexually transmitted diseases may cause blockages at the sperm ducts. The patient may have normal production of sperm, but the ducts carrying it are obstructed.

Active bacterial or viral infections may have a negative effect on sperm production or sperm function. White blood cells, which are the body’s response to infection, may also have a negative effect on sperm membranes making them less hearty.

If excessive white blood cells or bacteria (more than 1 million/cc) are seen in a semen specimen, cultures should be done. This usually includes cultures for commonly asymptomatic, sexually transmitted diseases including mycoplasma, ureaplasma and chlamydia. Also, a general genital culture is usually taken. If the infection and the white blood cells are persistent then antibiotics may be considered.

It is important to note that in most men the ejaculate is not sterile. In controlled studies, the average man will culture positive for approximately two organisms. It is therefore very important to be judicious in the treatment of non-sexually transmitted organisms found on cultures.

When these conditions are treated, a man will often see a significant improvement in his semen analysis.

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