The sixth edition of the "WHO Laboratory manual for the examination and processing of human semen" (2021) defines oligozoospermia as the presence of less than 16 million spermatozoa per milliliter of semen and/or less than 39 million spermatozoa in the total ejaculate.
Spermatogenesis (production and development of spermatozoa) occurs in both testicles at the same time, begins at puberty and does not cease throughout the individual's life. It is estimated that every three months there is a complete renewal of the sperm line. Several factors are involved in the production and development of spermatozoa, among the main ones are genetic, hormonal, metabolic and environmental.
For normal spermatogenesis, an adequate hormonal environment is required both locally and systemically. In fact, the testicle, besides being the "factory" of spermatozoa, is an endocrine gland that produces androgens (male steroid hormones) which are directly involved in sperm production and development. On the other hand, there are hormones produced in the pituitary gland such as FSH and LH, which are responsible for activating and maintaining sperm production.
Consequently, if there is a low FSH release it could produce a decrease in the number of spermatozoa and if there is a decrease in the release of LH it would trigger an alteration in the generation of androgens at the testicular level, which would also result in an alteration in the production of spermatozoa.
From the above mentioned, it can be deduced that spermatogenesis depends to a great extent on hormonal actions, therefore, if there is any hormonal alteration, it will have repercussions on sperm production, which can lead to oligozoospermia, even azoospermia (total absence of spermatozoa).
It is especially important to look for the causes of oligozoospermia because knowing the origin of the problem in some cases it is susceptible to medical treatment. This is especially useful in hormonal disorders, which justifies performing hormonal determinations in cases of low sperm count to try to find the cause of this problem and solve it.
