en Obstetrics & Gynicology Obstetrics & Gynicology Original Article Original Article <span style="font-size:14px;"><span style="font-family:Times New Roman;"><span style="line-height:14pt"><b><i><span style="color:blue">Background</span></i></b><i><span style="color:blue">:</span></i> Vitamin D is associated with numerous disorders, including infertility. Accordingly, the goal of this research was to find out the level of vitamin D and messenger RNA (mRNA) expression of vitamin D receptor (VDR) in the sperm of male subjects with unexplained infertility.<span style="font-size:9.0pt"></span></span><br> <span style="line-height:14pt"><b><i><span style="color:blue">Methods:</span></i></b> Twenty-four unexplained infertile men as the case group and 22 healthy fertile men as the control group were recruited. Vitamin D levels were evaluated in seminal fluid using enzyme-linked immunosorbent assay (ELISA). Afterwards, the swim-up test was performed to isolate motile sperm cells. From these cells, RNA was extracted, complementary DNA (cDNA) was synthesized, and mRNA expression of the VDR gene was evaluated with quantitative real-time polymerase chain reaction (PCR).</span><br> <span style="line-height:14pt"><b><i><span style="color:blue">Results:</span></i></b> A decrease in VDR mRNA expression levels was detected in the case group compared to the control group, but this reduction was not statistically significant (p>0.05). Besides, the level of vitamin D in seminal fluid was not detectable in both groups.<b><i><span style="color:blue"></span></i></b></span><br> <span style="line-height:14pt"><b><i><span style="color:blue">Conclusion</span></i></b><i><span style="color:blue">:</span></i> The sperm of unexplained infertile men express VDR gene mRNA, although there was no vitamin D in seminal samples. Hence, vitamin D and VDR signaling might not be effective in the etiopathogenesis of unexplained infertility in men.<b><i><span style="color:#0033cc"></span></i></b></span></span></span> vitamin D receptor, unexplained infertility, vitamin D, mRNA expression 94 99 http://caspjim.com/browse.php?a_code=A-10-792-1&slc_lang=en&sid=1 Zahra Akbari Sagheb narjeskhatoone@yahoo.com 100319475328460040842 100319475328460040842 No Infertility and Reproductive Health Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran Mousa Mohammadnia-Afrouzi m.mohammadnia@mubabol.ac.ir 100319475328460040843 100319475328460040843 No Infertility and Reproductive Health Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran Hamid Shafi dr_hamidshafi@yahoo.com 100319475328460040844 100319475328460040844 No Infertility and Reproductive Health Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran Sedigheh Esmaelzadeh sesmael@yahoo.com 100319475328460040845 100319475328460040845 No Infertility and Reproductive Health Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran Kousar Smailnejad Ganji ksganji70@gmail.com 100319475328460040846 100319475328460040846 No Cellular and Molecular Biology Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran Mehdi Shahbazi mehdishahbazi60@yahoo.com 100319475328460040847 100319475328460040847 Yes Immunoregulation Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran