. 2020 Sep 11;12(9):2791. doi: 10.3390/nu12092791

Table 2.

Prospective studies on AITD and VitD supplementation.

Authors Study Type	Number of Subjects and Intervention	Results	Effect on Ca²⁺/PTH
Chaudhary S. et al. 2016 [91] Open-label RCT	One hundred and two AITD subjects randomized to receive cholecalciferol 6000 IU + calcium 500 mg/d (G1) or only calcium (G2) Positive response defined as a decrease ≥ 25% in anti-TPO titers.	Response in 68% of G1 vs. 44% of G2 Only significant in those with TSH ≤ 10 mUI/mL.	Higher PTH in those with lower 25(OH)D₂, no statistically significant difference in Ca²⁺ and P^- levels. PTH reduction after supplementation.
Krysiak R. et al. 2016 [95] Longitudinal, Case–Control trial	Thirty-eight PPT vs. 21 healthy postpartum women. VitD supplementation in the subjects with PPT: -4000 IU/day if deficiency [25(OH)D < 20 ng/mL] -2000 IU/day or no supplement for the remaining patients	Lower baseline 25(OH)D levels in those with PPT. After supplementation of VitD according to baseline values→reduction in anti-TPO titers, with a more marked effect in those with deficiency at baseline.	Higher PTH and lower Ca²⁺ in those with PPT. Significant PTH reduction in those with a deficiency of 25(OH)D.
Simsek Y. et al. 2016 [96] Longitudinal, RCT	Eighty-two AITD patients -46 were supplemented with VitD 1000 IU/day for 1 month -36 were not supplemented	Reduction in anti-TPO and anti-Tg titers only in the supplementation group.
Krysiak R. et al. 2017 [92] Longitudinal, Case–Control trial	Thirty-two women with HT, euthyroid, or with sub-clinical hypothyroidism and 25(OH) > 30 ng/mL -18 were supplemented with VitD 2000 UI/day for 6 months -16 were not supplemented	At baseline: inverse correlation of 25(OH)D with antibody titers with non-significant difference between groups. At 6 months: reduction in antibody titers (mainly anti-TPO) in relation to the increase in 25(OH)D only statistically significant in those with sub-clinical hypothyroidism (vs. euthyroidism) and dependent on baseline antibody titers.
Krysiak R. et al. 2019 [93] Non-randomized	Thirty-two men with AITD in euthyroidism -20 supplemented with VitD 4000 IU/day -17 with selenomethionine 200 μg/day	Similar reduction in anti-TPO and anti-Tg titers in both groups. Greater effect of VitD on antibody titers in those with 25(OH)D < 30 ng/mL (~75 nmol/L) at baseline.
Mazokopakis E. et al. 2015 [90] Non-randomized	From a group of 218 HT, the 186 with 25(OH) < 30 ng/mL were supplemented with cholecalciferol 1200–4000 IU/day.	Negative correlation between baseline 25(OH)D and anti-TPO. Significant decrease in anti-TPO after 4 months of supplementation.	No statistically significant difference in Ca²⁺ and P^- at baseline or after supplementation.
Vondra K. et al. 2017 [41] Non-randomized	Thirty-seven women with AITD were supplemented with 4300 IU/day of cholecalciferol for 3 months.	Positive relationship between fT4/fT3 ratio in patients with AITD and 25(OH)D deficiency which disappeared after supplementation with cholecalciferol.	Correlation with higher PTH and lower Ca²⁺ at baseline. Normalization after supplementation.

Legend: AITD, autoimmune thyroid disease; anti-Tg, anti-thyroglobulin; anti-TPO, anti-thyroid peroxidase; fT3, free triiodothyronine; fT4, free thyroxine; G1, group 1; G2, group 2; PPT, post-partum thyroiditis; PTH, parathyroid hormone; RCT, randomized controlled trial; VitD, vitamin D; TSH, thyroid stimulating hormone.