The Effect of Vitamin D Consumption During Pregnancy on Maternal Thyroid Function and Depression: A Randomized, Placebo-Controlled, Clinical Trial

Background: Beyond the vital function of vitamin Din the homeostasis of calcium balance, possible widespread effects of vitamin D are shown in numerous studies. Objectives: The current study aimed at evaluating the effects of vitamin D supplement on thyroid function and postnatal depression. Methods: In the current randomized experimental study, the vitamin D group presented with two1000 IU vitamin D3 pills (2000 IU) daily from 26th to 28th week of gestation until birth; however, the control group received placebo. Inter- and intra-group comparisons were performed in terms of maternal serum level of 25-hydroxyvitamin D, thyroid-stimulating hormone (TSH), free thyroxine (FT4), and thyroid peroxidase (TPO), and 4th week postnatal depression score. Results: At birth, changes in maternal serum level of 25-hydroxyvitamin D was significantly different between the two groups (P = 0.004). The two study groups were not different significantly in terms of TSH, FT4, and TPO levels at birth (P > 0.05). While, at 4th week postnatal, depression score was significantly different between the two groups (P = 0.002). Conclusions: Vitamin D, 2000 IU /day in late pregnancy could induce a significant difference in the 4th week postnatal depression score independent of thyroid function.