The reduced number of semen production is one of the predominant causes of infertility in males. Semen may contain few spermatozoa (oligozoospermia) or no spermatozoa (azoospermia) due to problems in its production in the testicles. The prominent causes for low semen production are due to:
Disorder of the brain glands (Hypophysis and Hypothalamus that generate the hormones regulating the formation of spermatozoa), Genetic disorders (Klinefelter syndrome, alteration of genes contained in the Y-chromosome that regulates the formation of spermatozoa, other numerous testicular problems, such as underdevelopment, anomalous development, failure to descend into the scrotum (cryptorchidism), trauma, and inflammations (whether sexually transmitted or otherwise), tumors, exposure to toxic substances, chemotherapy and radiotherapy and varicocele.
Spermatozoa may not be found or found in very low numbers in semen because of the obstructions in their path from the testicles to the urethra owing to various reasons. They are
Spermatozoa can also show anomalies in their motility(astenozoospermia), shape(teratozoospermia) or vitality(necrozoospermia) due to different causes relating to 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).
The quality and count of the sperms can also be affected by major diseases such as diabetes, thyroid disorders, kidney disease and hepatic insufficiency, as well as the intake of certain medications, tobacco and stress.
Genital tract disorders stop semen from being deposited in the vagina during intercourse (erectile impotence, absence of ejaculation). In addition, there could be an abnormal situation of the urinary meatus like