The role of vitamin D in impaired fertility treatment.

Vitamin D is currently in the scope of research in many fields of medicine. Despite that its influence on health remains uncertain. This paper presents the review of the publications concerning the role of calciferol in reproduction processes and its significance in infertility therapy covering topics of polycystic ovary syndrome, endometriosis infertility, myoma infertility, male infertility, premature ovary failure and in vitro fertilization techniques. The results of latest research articles in those fields has been discussed and summarized. The deficiency of vitamin defined as the concentration of 25-hydroxycalciferol <20 ng/ml is frequently noted in patients of fertility clinics. Serum vitamin D concentration in healthy women is higher comparing to PCOS patients. The supplementation with vitamin D should be applied in the schemes of PCOS treatment both due to an improved insulin resistance and the results of infertility treatment. The explanation of vitamin D activity mechanism in patients with PCOS requires further research. Vitamin D have direct effect on AMH production, and thus increase longer maintenance of ovarian reserve in the patients with its higher concentration. The occurrence of uterine myomas in the group with vitamin D deficiency was evaluated as much higher comparing to controls. On the other hand it is supposed that high concentration of calciferol may be related to an impaired elimination of endometrial cells passing to peritoneal cavity via ovarian reflux causing endometriosis. In male infertility both low (<20 ng/ml) and high (>50 ng/ml) concentration of vitamin D in serum negatively affects spermatozoa number per ml of semen, their progressive movement and morphology. Significant differences as a response on ovulation stimulation, number and quality of embryos depending on vitamin D concentration were not observed in none of the analyzed papers concerning the role of vitamin D in in vitro fertilization (IVF). Better results in patients without calciferol insufficiency are explained by reports about high concentration of vitamin D and its metabolites in human in decidua collected in the 1st trimester of pregnancy which suggests its contribution in proper implantation and local immunological preference of the embryo. It is accepted that the treatment requires vitamin D concentration below 20 ng/ml (up to 50 nmol/l), especially in obese women, these with insulin resistance and small ovarian reserve and in men with oligo- and asthenozoospermia.