Prolactin and spermatogenesis: new lights on the interplay between prolactin and sperm parameters

Purpose: To clarify the relationship between one the most gender-specific hormone, i.e. prolactin (PRL), and semen parameters in men. Methods: A retrospective, observational, cohort, real-world study was carried out, enrolling all men performing a semen analysis and PRL examination from 2010 to 2022. For each patient, the first semen analys was extracted, associated to PRL, total testosterone (TT), follicle stimulating hormone (FSH) and luteinizing hormone (LH). Hyperprolactinaemia (>35 ng/mL) was excluded. Results: 1211 subjects were included. PRL serum levels were lower in normozoospermia compared to azoospermia (p = 0.002) and altered semen parameters (p = 0.048) groups. TT serum levels were not different among groups (p = 0.122). Excluding azoospermic men, PRL serum levels were lower in normozoospermic patients, when compared to other groups of semen alterations. An inverse correlation was detected between PRL and sperm concentration. Considering normozospermic subjects, PRL was directly related to both non-progressive sperm motility (p = 0.014) and normal sperm morphology (p = 0.040). Subdiving the cohort in quartiles according to PRL distribution, the highest motilities were observed in the second PRL quartile (8.30-11.10 ng/mL) and asthenozoospermia was significantly predicted by FSH (p < 0.001) and second PRL quartile (p = 0.045). Conclusion: The PRL-spermatogenesis connection seems to be mild, although low-normal PRL levels are associated with the best spermatogenetic profile. PRL serum levels could mirror the immunoregulatory status within the testis, suggesting that there is a sort of 'PRL optimal window' reflecting an efficent spermatogenesis. Alternatively, men with good semen parameters might have a higher central dopaminergic tone resulting in low PRL levels.