To date, the key role of vitamin D in male reproductive system has been suggested, since the expression of vitamin D receptors and metabolizing enzymes was demonstrated in the testis and spermatozoa. Nevertheless, a general consensus about the role of vitamin D in male fertility is still debated. The aim of this review is to provide an updated systematic revision of the current available literature, discussing the experimental and clinical evidence on the role of vitamin D in the regulation of testis hormone production, seminal parameters and male fertility. The consequences of vitamin D deficiency on serum levels of testicular hormones have been analysed by several observational and interventional studies, with controversial results. Equally, the experimental researches not were able to state a certain relationship between vitamin D status and testis hormone production. Possible bias, including age, body mass index, and baseline vitamin D status justified the differences among studies. As well as concerning the effect of vitamin D on semen parameters, most of the studies agreed in the possibility that vitamin D might have a positive effect on human male fertility potential, particularly through better sperm motility. Regarding pregnancy outcomes, normal level of vitamin D seems to be related to better pregnancies. However, all the previous studies displayed a wide heterogeneity in study design, population, methodology, and cut off values used for the evaluation of vitamin D status. Future studies are needed to better clarify the exact role of vitamin D on hormonal and seminal panel in both fertile and infertile men.

The world journal of men’s health. 2019 May 17 [Epub ahead of print]

Gianmartin Cito, Andrea Cocci, Elisabetta Micelli, Alejandro Gabutti, Giorgio Ivan Russo, Maria Elisabetta Coccia, Giorgio Franco, Sergio Serni, Marco Carini, Alessandro Natali

Department of Urology, Careggi Hospital, University of Florence, Florence, Italy. ., Department of Urology, Careggi Hospital, University of Florence, Florence, Italy., Department of Gynecology and Obstetrics, St. Claire Hospital, University of Pisa, Pisa, Italy., Department of Radiology, Salvador Zubirán National Institute of Health Sciences and Nutrition, Mexico City, Mexico., Department of Urology, Vittorio Emanuele II, University of Catania, Catania, Italy., Assisted Reproductive Technology Centre, Careggi Hospital, University of Florence, Florence, Italy., Department of Urology, “La Sapienza” University of Rome, Rome, Italy.