Pre-testicular causes
We refer to those causes related to sperm formation in an indirect way, such as the level of hormones secreted by the pituitary. General health issues are also related to this aspect, such as food habits or smoking and drinking alcohol: they all can alterate the good organism functioning.

Testicular causes
They refer to some alterations connected to the testicles, like cryptorchidism, hydrocele, genital injuries, varicocele; or also to some genetic alterations with a testicular effect, like microdeletions in the Y chromosome.

Post-testicular causes
Even if the sperm is synthesized within the testicles in a correct way, an obstruction can occur and prevent a normal ejaculation. For example, an obstruction in the vas deferens, the absence of these ones, or inflammations in the urethra, which can prevent seminal fluid release.

Reversible or permanent oligospermia?
Oligospermia is usually permanent, whenever the origin of its emergence is:
-- Genetic problems, Y chromosome alterations or an abnormal karyotype.
-- Atrophy of the seminiferous tubules (the part of the testicles where sperm are produced).
-- Related chronic diseases.