Alterations in semen production
A decrease in amount and/or quality of the spermatozoa.
Semen may contain few spermatozoa (oligozoospermia) or no spermatozoa (azoospermia) due to problems in production of it 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 not, tumours, exposure to toxic substances, chemotherapy and radiotherapy, varicocele, etc.)
Spermatozoa may also be absent or 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), oxidization phenomena, varicocele (anomalous dilation of veins that come out mainly from the left testicle), etc.
There are many other causes that might affect the number and quality of spermatozoa. Among these, it is worth mentioning 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 stressful situations.
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.