In about half of all unintentionally childless couples, the cause of the fertility problem lies solely or partly with the man. Often this is discovered only by examination of a semen sample in the laboratory.
Many different factors can limit male fertility – up to and including infertility (infertility). Often, however, the exact causes remain in the dark. Partly because the process of sperm maturation, the transport of sperm to the egg and the complex fertilization process is still not known in all details. Partly because so many hormonal and enzymatic processes have to interact in the male that it is often impossible to say at which point exactly the maturation or fertilization process is disturbed. Therefore, even if the results of a sperm test (spermiogram) are normal, the sperm may not be able to fertilize without medical assistance.
Disorders of spermatogenesis
The most common male fertility disorder is that not enough intact and well-moving sperm are produced. As a guideline, the total number of sperm in the seminal fluid (ejaculate) should be at least 39 million (or 15 million per milliliter), of which at least four percent should be normally shaped and at least 32 percent should be well motile.
The cause of the disorder can be a previous or current undescended testicle (inguinal or sliding testicle etc.).). In this case, the testicles are not completely or consistently located in the scrotum, as required for undisturbed sperm production. The probable genetic causes of undescended testicles have not yet been clearly established. The defective position damages the testicles in the long run, because they are too warm and possibly also have a poorer blood supply. As a result, they produce too few sperm.
Direct damage to the testicular tissue can also have a lasting effect on sperm production: This can be caused by previous or acute infections of the testicles or epididymis (orchitis/epididymitis), which also includes mumps orchitis in childhood. Damage can also be caused by injuries to the testicles, e.g. through sports, or by testicular torsion. Last but not least, varicoceles (thickened veins mostly in the left half of the scrotum) are suspected of disrupting sperm production.
Testicular tumors are rare overall, but are among the most common male cancers in the 20-40 age group. Testicular tumors are also much more common among men with an established fertility disorder. The fertility disorder is therefore also considered a risk factor for tumor disease of the testis.
Smoking has been shown to have a detrimental effect – both on sperm production and on the ability to fertilize the sperm. Due to increased DNA damage to the sperm, the chances of success of artificial insemination are also reduced in smokers.
Sperm transport disorders
In some men, although sufficient sperm are produced. Due to a disturbance of the sperm transport – the seminal ducts are partially or completely closed or not fully formed – they cannot mix with the sperm fluid. In these cases, too few or no intact sperm are found in the ejaculate (obstructive azoospermia).
The cause is often a disturbance of the epididymal function, scarring of the vas deferens – for example, due to surgery for a hernia or intentionally due to sterilization (vasectomy) – or a congenital malformation. Unnoticed infections (such as those caused by chlamydia) can also lead to blockage of the vas deferens.
In many cases, blocked seminal ducts can be opened microsurgically, so that conception is possible again naturally. If the seminal ducts cannot be made passable, there is the possibility of testicular sperm extraction (TESE) or microsurgical epididymal sperm aspiration (MESA). Sperm are removed from the testicles or epididymis, frozen and later processed for artificial insemination.
Insufficient urinary bladder obstruction
In some men, the muscular closure between the bladder and the prostate does not function adequately, resulting in so-called retrograde ejaculation. During orgasm, semen is not expelled through the penis, but is released into the bladder and later excreted in the urine.
Possible causes of inadequate urinary bladder obstruction include surgery on an enlarged prostate, diabetes mellitus, or nerve damage. If retrograde ejaculation itself cannot be treated, it may be possible to filter the sperm out of the urine using special procedures.
In immunological sterility, the man’s immune system treats his own sperm cells as foreign bodies. The result is a defense reaction against the body’s own cells (autoimmune reaction). The immune system attacks the sperm cells by producing antibodies against them in the blood. These antibodies attach to the sperm and can impair both their motility and their ability to reach the egg and penetrate its coating.
In reproductive medicine, it is controversial whether the formation of antibodies alone is sufficient to decisively limit fertility. However, it must be assumed that serious impairment is likely if more than 50% of the sperm are contaminated with antibodies.
The significance of environmental influences, such as pesticides, organochlorine compounds and other chemical substances, heavy metals, radioactive radiation or heat, is unclear. Although the damaging effect on the human body is undisputed above a certain level, a clear influence on fertility can rarely be proven for individuals. Nevertheless, the conditions at home and at work should be taken into consideration when looking for fertility-disrupting influences.
In addition, there are a number of hormonal and genetic disorders that can affect male fertility in a variety of ways. In addition, the ability to procreate can be hindered by ejaculation disorders and erection problems.
Last but not least, general diseases of the kidneys, heart and liver, metabolic disorders, as well as alcohol, drug and anabolic abuse can interfere with hormonal balance and initiate fertility-damaging processes.
In many cases (estimates range from 20 to 35 percent), reduced fertility can be identified, but not its exact cause. Then one speaks of the so-called idiopathic infertility. Behind this collective diagnosis, which remains when all known possible causes have been ruled out, lies a multitude of previously unidentifiable disorders in the control of sperm production and the fertilization process.
Treatment is often possible
At the time of diagnosis, the causes of a fertility disorder are often out of one’s control. The problem is often caused by an early developmental disorder (e.g. undescended testicles) or an (unnoticed) past infection of the testicles or spermatic ducts.
Yet medicine can often offer help. Basically, it is important to identify possible causes for the fertility disorder and to treat them if possible. For example, if hormonal control of testicular function is disrupted, it is often possible to replace the missing hormones or correct excessive production of hormones.
If fertility cannot be improved or if the causes of the fertility disorder are not treatable, it is possible to make it easier for the egg and sperm to find each other. This is done with the help of artificial insemination techniques (ART). They do not eliminate the cause of a fertility disorder, but they help to circumvent the effects of a disorder on the ability of the sperm to fertilize. Which procedure is appropriate depends on both the man’s and the woman’s findings. The decision always affects the couple as a whole.
ART procedures include intrauterine insemination (IUI), in vitro fertilization (IVF), and most importantly, intracytoplasmic sperm injection (ICSI).