Vitamin D and follicular recruitment in the in vitro fertilization cycle

Vitamin D (VD) is a fat-soluble steroid hormone, synthesized by the skin, most known for its role in bone mineral balance. Vitamin D receptors (VDR) are also found in the female reproductive system, but their role remains unclear. The objective of this study was to analyze the relationship between serum vitamin D levels and the number of oocytes retrieved after ovarian stimulation. This is a retrospective study involving 267 patients undergoing in vitro fertilization (IVF) carried out in the Fertipraxis clinic, a private practice facility. The patients were initially divided into two groups according to their VD levels. Group 1 included 152 patients with VD levels < 30 ng/mL and group 2 had 115 patients with VD levels > 30 ng/mL. They were further analyzed and separated considering their age, anthropometric data, ovarian reserve, amount of gonadotropin used, and follicles obtained until trigger day. In our analysis, there were no difference in the number of follicles and oocytes retrieved, nor in the number of mature oocytes obtained from patients with both vitamin D deficiency and sufficiency. The results of our study show no difference among number of follicles, oocytes retrieved and mature oocytes obtained after ovarian stimulation according to their vitamin D serum levels. Further higher-quality studies are needed to evaluate the possible roles of serum vitamin D levels in other stages of human fertilization process.