Causes
Sperm disorders
Azoospermia
Azoospermia is an absence of sperm in the ejaculate. There are many causes of azoospermia, and not all are fully understood.Primary testicular failure is the most likely cause of azoospermia, and can be due to genetic defects, testicular injury or infection e.g. mumps or the failure of the testes to descend through the inguinal canal during development.
The testes are poorly developed and there is little chance of restoring fertility.Obstruction of the ducts that transport sperm from the testes to the urethra is the second major cause of azoospermia. Fully formed and perfectly healthy sperm may be produced, but they cannot mix with the rest of the seminal secretions and therefore cannot be ejaculated. Obstruction can be caused by sexually transmitted diseases such as gonorrhoea (Figure 1), or may be due to the absence of particular ducts linking the testes to the urethra e.g. the epididymis or vas deferens.
Patients suffering from cystic fibrosis often lack the vas deferens, and the remaining ducts are often blocked with mucous, resulting in infertility.In some cases of azoospermia, men lack spermatogenic germ cells, resulting in seminiferous tubules that only contain Sertoli cells. In majority of cases, the reason for this is unknown, but there may be links to fetal development such as exposure to drugs and irradiation.
Oligospermia
Oligospermia is a reduction in sperm count to less that 20 million per ml. Some of the causes of azoospermia, for example obstruction, are also causes of oligospermia. Environmental factors play a large role in the reduction of sperm count, for example smoking, alcohol, drugs and heat. There are also links to diet and other lifestyle options that may affect sperm count. Infections, such gonorrhoea, chlamydia or mumps can also affect sperm count – treatment with antibiotics can restore fertility providing the infection is caught quickly. If the infection is allowed to progress without treatment, it may result in sterility.
There are also a number of hormonal disorders that will result in a decrease in sperm count. Hypothalamic disorders, such as Kallman’s syndrome, are characterised by an absence of gonadotropin-releasing hormone. Pituitary disorders may be the result of tumours or surgical or radiation damage. Pituitary disorders have been associated with syndromes such as Prader-Willi syndrome, which is characterised by deficiencies of LH and FSH production.
Anatomical disorders
Erection and ejaculation
The inability to achieve an erection is known as impotence. If a man is suffering from impotence it does not also mean he is infertile, as sperm production and ejaculation may all be normal – however, failure to achieve an erection will make sexual intercourse very difficult, which will then lead to a failure to conceive. In many cases, the cause of impotence is psychological. However, some medications, such as antidepressants may result not only in impotence, but in a complete loss of libido.
Problems with ejaculation will result in a lack of sperm being deposited in the female tract, and the failure to conceive. Ejaculatory problems range from an inability to ejaculate, premature ejaculation or retrograde ejaculation.
The inability to ejaculate may be due to obstruction of the ducts leading from the testes into the urethra. There may also be psychological barriers to overcome – a case study of a 24-year-old man who was unable to ejaculate revealed that he believed he would father abnormal children if he did ejaculate. Another study of a 36-year-old man revealed that he believed he would be “spoiling” his wife if he ejaculated.
Premature ejaculation is more common in younger men, but can affect men of all ages. Not only is this likely to put a strain on the relationship and possibly result in a couple having sex less frequently, the inability to effectively deposit semen inside the vagina will result in an inability to conceive.
The cause of premature ejaculation is not entirely certain, although in many cases nerves and anxiety play a role.Retrograde ejaculation is rare and accounts for ~1% of cases of male infertility. It is due to the semen being pushed back into the bladder instead of exiting through the penile urethra. It is caused by the inability of the bladder sphincter to contract properly and prevent the backwards movement of the sperm. This can be due to antidepressant medication or previous surgery to the prostate.