The man is fundamentally responsible for infertility, or shares the causes with the woman, in approximately 50% of cases. To study male fertility, an analysis is carried out, testing the number, activity and shape of the spermatozoa. A normal result would be a sperm count higher than 20 million/millilitre, with at least 50% of the spermatozoa having correct motility and 30% having a normal shape.

Basically, the male reproductive function requires normal sexual functioning (erection and ejaculation) and normal sperm functioning (spermatozoa)

The main disorders are:

Genital tract disorders

This prevents semen from being deposited at the back of the vagina during coitus (erectile impotence, absence of ejaculation).

In addition there is an anomalous situation of the urinary meatus, whether below its normal location (hypospadias) or above it (epispadias), a penis with a curvature that is a too pronounced or a big decrease in its size, and extreme obesity. Serious erection problems, premature or delayed ejaculation and other ejaculation problems (ejaculation towards the urinary bladder or lack of ejaculation) can also prevent the spermatozoa from being adequately deposited in the vagina.

Alterations in semen productionA decrease in the amount and/or quality of the spermatozoa.

Semen may contain few spermatozoa (oligozoospermia) or no spermatozoa (azoospermia) due to problems in its production in the testicles. The main causes may be found in the brain glands (hypophysis and hypothalamus) which produce the hormones regulating the formation of spermatozoa, in genetic disorders (Klinefelter syndrome, alteration of the genes contained in the Y-chromosome that regulate the formation of spermatozoa, etc.) or in a great number of testicular problems: lack of development, anomalous development, failure to descend into the scrotum (cryptorchidism), trauma, inflammations (whether sexually transmitted or otherwise), tumours, exposure to toxic substances, chemotherapy and radiotherapy, varicocele, etc.).

Spermatozoa may also be absent or may be present in very low numbers in semen because of obstructions in their path during their journey from the testicles to the urethra, due to various reasons: absence of part of the conduits (frequently associated to the cystic fibrosis gene), inflammations, tumours, trauma, involuntary surgical lesions, vasectomy, etc.

Spermatozoa can also show anomalies in their motility (astenozoospermia), shape (teratozoospermia) or vitality (necrozoospermia) due to different causes: infections, presence of antibodies (which act against spermatozoa), DNA fragmentation (genetic material contained in the spermatozoid’s head), oxidation phenomena, varicocele (anomalous dilation of veins that come out mainly from the left testicle), etc.

There are many other causes that can affect the number and quality of spermatozoa. Among these are major diseases such as diabetes, thyroid disorders, kidney disease and hepatic insufficiency, as well as the intake of certain medication (negative side effects on hormones, on sexuality, on testicles, etc.), drugs, tobacco and stress.

It must be taken into account that, in many cases, spermatozoa and their precursor cells are highly sensitive and easily affected by many factors that are very often difficult to identify.