Vitamin D and TSH: Do Their Level Impact on IVF outcomes?

Abstract Abstract: There is a positive correlation between serum 25 (OH) Vit D concentrations below 30 ng/ml and the incidence of preterm delivery, while higher levels can bring benefits to pregnancy. Although studies agree that TSH levels affect fertility, in euthyroid women (0.5<TSH<4.5), the serum concentration of this hormone still has a dubious effect on gestational outcomes. In order to study the relationship between vitamin D, TSH levels and pregnancy endpoint, a retrospective cohort study was conducted that considered 520 women who had undergone In-Vitro Fertilization (IVF). Patients were grouped regarding TSH values in mIU/L: 0.5-2.49 (Group 1) (n=416) and 2.5-4.5 (Group 2) (n=104), the serum levels of 25 (OH) Vit D within them were dichotomized in subgroups: <30 ng/mL (Group 1, n=212; Group 2, n=49) and >30 ng/mL (Group 1, n=204; Group 2, n=55). Primary endpoint was clinical pregnancy (the presence of the gestational sac and fetal heartbeat by ultrasound) and secondary outcomes were miscarriage and gestacional age (preterm or full-term pregnancy). The rate of clinical pregnancy in group 1 was significantly higher in patients with 25 (OH) Vit D <30 ng/ml (51.9%) than 25 (OH) Vit D >30 ng/ml (42.2%) according to the chi-square test and Fisher’s exact test (p<0.05 all). There was no significant difference in group 2 (p=0.35), with percentages of 49% and 40% in the respective subgroups. Moreover, no statistical difference between the abortion rates was seen in 25 (OH) Vit D subgroups in groups 1 (p=0.71) and 2 (p=0.52). When gestational age rates were measured, the percentage of full-term pregnancies was lower in patients with 25 (OH) Vit D <30 ng/ml (Group 1=62.6%; Group 2=57.9%), compared to those with 25 (OH) Vit D >30 ng/ml (Group 1=77.6%; Group 2=78.9%), however, only the subgroups in the TSH category between 0.5-2.49 mUI/L showed a statistically significant difference (p<0,05). The Spearman test identified a weak positive correlation between 25 (OH) Vit D and gestational age (ρ=0.218; p<0.05). The findings indicate lower frequency of clinical pregnancy in patients with TSH between 0.5-2.49 mIU/L and 25 (OH) Vit D >30 ng/ml. In addition, variations in 25 (OH) Vit D, in both TSH groups, do not suggest interference in miscarriage rates. Furthermore, higher serum concentrations of 25 (OH) Vit D seem to be involved with an increase in the prevalence of full-term births, an important finding to guide the procedures for IVF.