Table 1.

Characteristics of the included trials and participants.

Included trials	Country	Total participants (T/C)*	Baseline thyroid function	Baseline vitamin D status†	Baseline 25(OH)D levels (T vs C)
Huang, 2013[51]	China	32 (16/16)	Hypothyroidism	Insufficiency	15.86 ± 3.56 vs 16.50 ± 2.81 ng/mL
Han et al, 2015[50]	China	62 (32/30)	Hypothyroidism	Not restricted	17.91 ± 6.59 vs 18.22 ± 5.19 ng/mL
Zhao et al, 2016[48]	China	36 (18/18)	Hypothyroidism	Insufficiency	16 ± 4 vs 16 ± 3 µg/L
Parichehr Vahabi Anaraki et al, 2017[36]	Iran	65 (33/32)	Hypothyroidism	Deficiency	12.76 ± 0.74 vs 13.28 ± 0.86 ng/mL
Zhou et al, 2018[49]	China	122 (61/61)	Euthyroidism or Subclinical Hypothyroidism	Deficiency	29.50 ± 19.65 vs NR‡ nmol/L
Zuo et al, 2018[45]	China	70 (35/35)	Euthyroidism	Deficiency	10.61 ± 1.30 vs 13.58 ± 1.18 nmol/L
Fu et al, 2019[34]	China	70 (36/34)	Euthyroidism or Subclinical Hypothyroidism	Insufficiency	15.08 ± 3.23 vs 13.99 ± 2.32 µg/L
Reza Chahardoli et al, 2019[31]	Iran	42 (21/21)	Hypothyroidism	Not restricted	25.38 ± 11.02 vs 19.80 ± 8.81 ng/mL
Jia, 2020[47]	China	102 (51/51)	Hypothyroidism	Not restricted	17.89 ± 6.38 vs 19.10 ± 6.51 ng/mL
Xiao et al, 2020[44]	China	80 (40/40)	Euthyroidism	Deficiency	14.60 ± 5.08 vs 15.29 ± 6.88 ng/mL
Zhang, 2020[46]	China	90 (45/45)	Hypothyroidism	Deficiency	17.16 ± 6.45 vs 18.24 ± 4.36 ng/mL
Zhao, 2022[33]	China	98 (49/49)	Euthyroidism or Subclinical Hypothyroidism	Insufficiency or Deficiency	15.64 ± 5.54 vs 16.98 ± 5.43 ng/mL

^*T: Treatment Group, C: Control Group.

^†Vitamin D Status: > 30 ng/mL (75 nmol/L) for sufficiency, 20–30 ng/mL (50–75 nmol/L) for insufficiency, < 20 ng/mL (50 nmol/L) for deficiency.

^‡Not reported.