What is the purpose of the prostate gland in the male reproductive system?

The Prostate's Role in Male Reproduction

The prostate gland produces prostatic fluid that comprises approximately 30% of semen volume and contains essential substances—including zinc, citrate, enzymes (particularly kallikreins), and prostasomes—that activate sperm, protect them from the female immune system, and enable successful fertilization. 1, 2

Primary Functions of the Prostate

Secretory Function

• The prostate secretes prostatic fluid enriched with zinc (Zn²⁺), citrate, and kallikreins that is crucial for the molecular synchronization of the functional cascade triggered by ejaculatory stimuli 2
• Prostatic fluid provides enzymes, lipids, amines, and metal ions essential for normal spermatozoa function 1
• The secretions combine with fluids from the testes, epididymis, seminal vesicles, and bulbourethral glands to create semen that supports sperm survival and provides a medium for sperm transport through the reproductive ducts 3

Prostasome Production and Sperm Protection

• Epithelial cells lining the prostate acini release nanosized organellar structures called prostasomes through exocytosis 4
• Prostasomes protect sperm cells against immune response in the female reproductive tract by modulating the complement system and inhibiting monocyte and neutrophil phagocytosis and lymphocyte proliferation 4
• These structures contain small non-coding RNAs and various transferable bioactive molecules (receptors and enzymes) that promote the fertilizing ability of sperm cells 4

Regulation of Sperm Capacitation

• Prostasomes regulate the timing of sperm cell capacitation and induction of the acrosome reaction, which are critical steps for successful fertilization 4
• The prostate's zinc and citrate content plays a central role in regulating prostate epithelium homeostasis and proper ejaculation function 2

Clinical Significance for Male Fertility

Impact of Prostatic Disease

• Prostatic diseases or an unhealthy prostate can affect spermatozoa functioning and male fertility in both young and aged men 2
• Prostatitis, the most common prostate disorder, can severely impair reproductive health and significantly influence sperm function and overall male fertility 5
• Bacteria-related prostatic inflammation influences male fertility and may promote the development of prostatic hyperplastic growth and carcinogenesis 2

Diagnostic Considerations

• Low ejaculate volume (<1.4 mL) with acidic semen (pH <7.0) and azoospermia or severe oligospermia suggests ejaculatory duct obstruction, which prevents prostatic fluid from entering the ejaculate 6
• Transrectal ultrasonography (TRUS) is indicated in patients who are azoospermic with palpable vasa and low ejaculate volumes to determine if ejaculatory duct obstruction exists 7

Common Pitfalls

• Do not overlook the prostate when evaluating male infertility—most research has focused on testicular function while ignoring the critical role of prostatic secretions in sperm viability and function 5
• Recognize that prostasomes represent a new category of sperm antigens—circulating antisperm antibodies recognize prostasomes, with prolactin-inducible protein (95%) and clusterin (85%) being immunodominant antigens that may contribute to immunological infertility 4
• Treat male accessory-gland infections when identified, as this may improve sperm quality, though it does not necessarily improve the probability of conception 7