The Process of Sperm Production
In the **testes**, the seminiferous tubules are lined with **5 to 8 layers of cells**, consisting of both Sertoli cells and germ cells, collectively known as the germinal epithelium. The Sertoli cells are arranged along the basal membrane of the seminiferous tubules, extending towards the lumen. Their primary roles involve **support**, **nutrition**, and **protection** of the various stages of germ cells, and they may also play a role in regulating the interstitial cells. Germ cells undergo continuous proliferation and differentiation, progressing from spermatogonia to primary spermatocytes, then secondary spermatocytes, and finally to spermatids, leading to the formation of sperm. Each primary spermatocyte divides into four spermatids that attach to the recesses of the Sertoli cells for nourishment and undergo a maturation process to develop into sperm.
The Continuous Nature of Spermatogenesis
Spermatogenesis resembles an unending relay race, with sperm being produced at all times. The daily yield can reach **hundreds of millions** of sperm. Once fully developed, these sperm travel with testicular fluid into the epididymis. The process of spermatogenesis is primarily regulated by the hypothalamus, pituitary gland, and sex hormones.
Male Contraceptive Methods
Male contraceptive pills can exert their effects through various mechanisms:
- Long-term high doses of gonadotropin-releasing hormone (GnRH) can downregulate and lead to decreased secretion of pituitary gonadotropins (Follicle Stimulating Hormone and Luteinizing Hormone), thereby inhibiting spermatogenesis.
- Utilizing antibodies against Follicle Stimulating Hormone and Luteinizing Hormone can block their effects. However, since these two hormones share a common alpha subunit with Thyroid Stimulating Hormone, non-specific antibody action may cause unwanted side effects.
- Selective inhibition of the germinal epithelium using medications such as cottonseed oil occurred when researchers in China first discovered its contraceptive effects. This medication has gained significant attention internationally and is an oral contraceptive for men, offering affordability and ease of use, although it carries certain side effects. A common drawback of all male contraceptives is the slow onset of action, as these drugs do not kill already formed sperm. Furthermore, recovery of fertility after discontinuation may take time due to the lengthy spermatogenesis process.
- Using endogenous hormones like testosterone, either alone or combined with progestins, can inhibit the secretion of gonadotropins through negative feedback, thereby suppressing spermatogenesis. Regular injections of testosterone undecanoate have shown contraceptive effects and recovery potential post-treatment, marking it as a promising male contraceptive option.
All these medications interfere with the **hypothalamic-pituitary-gonadal** axis to disrupt the spermatogenesis process. However, they can be expensive and inconvenient to use while also affecting the function of testicular interstitial cells, leading to reduced testosterone levels, decreased libido, or erectile dysfunction. Consequently, further research is necessary to address these issues. Notably, although testosterone may suppress interstitial cell function, it provides a compensatory effect, maintaining sexual function and presenting a favorable outlook for its use in male contraception.