seminoma
Cryptorchidism
Varicocele (14% in one study)
Trauma
Hydrocele
Mumps
Malaria
Defects in USP26 enzyme in some casesMast cells releasing inflammatory mediators appear to directly suppress sperm motility in a potentially reversible manner, and may be a common pathophysiological mechanism for several of the above-mentioned factors. Post-testicular causes
Post-testicular factors decrease male fertility due to conditions that affect the male genital system after testicular sperm production and include defects of the genital tract as well as problems in ejaculation:

Vas deferens obstruction
Lack of Vas deferens, often related to genetic markers for cystic fibrosis
Infection, e.g. prostatitis
Ejaculatory duct obstruction

Idiopathic oligospermia (oligoasthenoteratozoospermia)
In about 30% of infertile men no causative factor is found for their decrease in sperm concentration or quality by common clinical, instrumental, or laboratory means, and the condition is termed "idiopathic" (unexplained). A number of factors may be involved in the genesis of this condition, including age, infectious agents ( such as Chlamydia trachomatis), Y chromosome microdeletions, mitochondrial changes, environmental pollutants, and "subtle" hormonal changes.A review in 2013 came to the result that oligospermia and azoospermia are significantly associated with being overweight (odds ratio 1.1), obese (odds ratio 1.3) and morbidly obese (odds ratio 2.0), but the cause of this is unknown. It found no significant relation between oligospermia and being underweight. DNA damage
The human breast cancer susceptibility gene 2 (BRCA2) is employed in homologous recombinational repair of DNA damages during meiosis.
In more severe cases IVF, or IVF - ICSI is done and is often the best option, specifically if time is a factor or fertility problems coexist on the female side. The Low dose Estrogen Testosterone Combination Therapy may improve sperm count and motility in some men including severe oligospermia. Fertility
Achieving a pregnancy naturally may be a challenge if the male has a low sperm count. However, chances are good if the female partner is fertile; many couples with this problem have been successful. Prognosis is more limited if there is a combination of factors that include sperm dysfunction and reduced ovarian reserve. See also
Conception device
Male infertility
Semen quality
Vasectomy


== References ==