Role of serum and gonadal fluid vitamin d levels and gonadal fluid vitamin d receptor levels in unexplained infertility cases

Vitamin D is a fat soluble vitamin with steroid hormone function that exerts its effects by binding to the nuclear vitamin D receptor (VDR). Besides its role on calcium-phosphorus metabolism, vitamin D has regulatory functions on various cellular metabolic processes, with crucial role in reproductive physiology. Its role in infertility is still unclear. The present study aims to evaluate if vitamin D concentrations in serum and/or gonadal fluid and VDR levels in gonadal fluid affect fertility in unexplained infertility cases treated with intracytoplasmic sperm injection (ICSI). Serum 25(OH) vitamin D concentrations from 76 partners were measured by tandem mass spectrometry (LC-MS/MS); gonadal fluid 25 (OH) vitamin D levels and gonadal fluid VDR levels were measured by chemiluminescent microparticle immunoassay (CMIA) and ELISA, respectively. Anti-Mullerian Hormone (AMH) concentrations in sera from female subjects were determined by paramagnetic particle chemiluminescent immunoassay; progesterone, estradiol, follicle stimulating hormone (FSH) and β-hCG levels to diagnose pregnancy were measured by CMIA. Pregnancy was (+) in 25 and (-) in 51 women after the ICSI cycle. Serum and gonadal fluid 25(OH) vitamin D levels were lower in pregnancy (+) women compared to that of pregnancy (-) women. However, follicular fluid VDR concentrations were significantly higher in pregnancy (+) women than that of non-pregnants. Serum 25(OH) vitamin D levels were lower in male partners of pregnancy (+) group compared to that of pregnancy (-) group while semen vitamin D and VDR concentrations were not different. Serum and follicular fluid vitamin D concentrations were significantly correlated in women but not in men. Female serum hormone concentrations were not different between groups. Results suggest that lower serum and/or follicular fluid vitamin D levels are not responsible alone as a factor of infertility; sufficient follicle VDR concentrations are also equally important to achieve pregnancy in ICSI treatment. Key words: Vitamin D, VDR, Unexplained infertility.