Background
Methods
Study design and population
Thyroid measures
Pure north program and vitamin D supplementation
Laboratory assessments
Participant subgroups
Statistical analysis
Results
Pure north population
Baseline demographics
Parameter | N | Percentage (%) |
---|---|---|
Age, years | 11,017 | 48 ± 16 (18–95 years) |
Gender | 11,017 | |
Female | 6378 | 58 |
Male | 4649 | 42 |
Body Mass Index, kg/m
2
| 10,554 | 27.6 ± 5.7 |
Normal weight (18.5–24.99) | 3730 | 35.3 |
Overweight (25–29.99) | 3807 | 36.1 |
Obese (≥30) | 3017 | 28.6 |
Medication history | 4411 | |
Desiccated thyroid (Armor thyroid) | 81 | 1.6 |
Synthroid | 592 | 13.4 |
Other thyroid medications | 100 | 2.3 |
Supplementation history | ||
Iodine | 1788/11,017 | 14.8 |
Magnesium | 446/8926 | 4.9 |
Niacin | 56/8779 | 0.6 |
Vitamin D | 4694/11,016 | 42.6 |
Thyroid Assessment Questionnaire | ||
Brain fog | 3761/10,176 | 37.0 |
Low energy level | 3643/6865 | 53.1 |
Macroglossia | 1343/9810 | 13.7 |
Low mood | 3534/10,147 | 34.8 |
Unrefreshing sleep | 4993/10,329 | 48.3 |
Cool body temperature | 3124/10,097 | 30.9 |
Weight gain | 2715/10,004 | 27.1 |
Serum 25(OH)D status, nmol/L | 11,017 | |
<50 | 2101 | 19.1 |
50–100 | 6660 | 60.4 |
100–150 | 1867 | 16.9 |
150–200 | 289 | 2.6 |
200–250 | 77 | 0.7 |
≥250 | 23 | 0.2 |
Comparison between baseline and follow-up
Parameter | N | Baseline (mean ± SD) | Follow-up (MEAN ± SD) | P-value |
---|---|---|---|---|
FT3 (pmol/L) | 11,017 | 4.9 ± 0.8 | 4.6 ± 0.2* | <0.001 |
FT4 (pmol/L) | 11,017 | 14.8 ± 2.9 | 13.5 ± 0.9* | <0.001 |
Anti-TPO (kU/L) | 11,017 | 32.2 ± 92.0 | 22.4 ± 41.0* | <0.001 |
Anti-TG (kU/L) | 11,017 | 40.1 ± 112 | 14.7 ± 28.7* | <0.001 |
TSH (mU/L) | 110,17 | 2.53 ± 2.1 | 2.13 ± 0.8* | <0.001 |
TG (µg/L) | 6509 | 29.2 ± 27.0 | 25.1 ± 5.0* | <0.001 |
hs-CRP (mg/L) | 10,968 | 2.71 ± 4.6 | 2.40 ± 2.2* | 0.04 |
25(OH)D (nmol/L) | 11,017 | 78 ± 34 | 110 ± 22* | <0.001 |
Vitamin D dose (IU/d) | 11,017 | 1436 ± 2543 | 4078 ± 2936* | <0.001 |
Vitamin D, thyroid measures, and inflammation
Relative risk (95% CI) based on serum 25(OH)D, nmol/L [n = 11,017] | Relative risk (95% CI) based on vitamin D supplement dose, IU/d [n = 11,017] | |||||
---|---|---|---|---|---|---|
<125 (n = 9796) | ≥125 (n = 1226) |
P valuea
| <4000 (n = 8215) | ≥4000 (n = 2806) |
P valuea
| |
FT3 decrease | 1.02 (1.002–1.029) | 0.88 (0.793–0.983) | 0.02 | 1.02 (1.003–1.049) | 0.93 (0.869–0.991) | 0.03 |
FT4 decrease | 1.56 (1.377–1.773) | 0.95 (0.938–0.963) | 0.01 | 1.39 (1.292–1.501) | 0.90 (0.882–0.921) | <0.001 |
Anti-TPO increase | 1.18 (1.158–1.202) | 0.32 (0.291–0.360) | <0.001 | 1.60 (1.545–1.653) | 0.34 (0.316–0.358) | <0.001 |
Anti-TG increase | 1.15 (1.132–1.172) | 0.37 (0.331–0.409) | <0.001 | 1.49 (1.445–1.536) | 0.37 (0.352–0.399) | <0.001 |
TSH increase | 1.07 (1.058–1.087) | 0.55 (0.495–0.621) | <0.001 | 1.20 (1.172–1.224) | 0.57 (0.536–0.615) | <0.001 |
TG increase | 1.02 (0.998–1.035) | 0.89 (0.776–1.015) | 0.08 | 1.04 (1.007–1.071) | 0.90 (0.832–0.978) | 0.01 |
hs-CRP increase | 1.12 (1.099–1.132) | 0.43 (0.385–0.479) | <0.001 | 1.28 (1.245–1.309) | 0.51 (0.477–0.543) | <0.001 |
Relative risk based on serum 25(OH)D, nmol/L (n = 3367) | Relative risk based on vitamin D supplement dose, IU/d (n = 3367) | |||||
---|---|---|---|---|---|---|
<125 (n = 2389) | ≥125 (n = 978) |
P valuea
| <4000 (n = 1001) | ≥4000 (n = 2366) |
P valuea
| |
Brain fog | 1.053 (1.007–1.10) | 0.88 (0.783–0.987) | 0.03 | 1.13 (1.012–1.25) | 0.95 (0.905–0.996) | 0.03 |
Macroglossia | 1.109 (1.023–1.204) | 0.75 (0.571–0.977) | 0.02 | 1.09 (0.866–1.34) | 0.97 (0.877–1.07) | 0.5 |
Low mood | 1.09 (1.042–1.144) | 0.79 (0.698–0.903) | <0.001 | 1.2 (1.07–1.34) | 0.92 (0.875–0.972) | 0.002 |
Unrefreshing sleep | 1.09 (1.046–1.14) | 0.80 (0.719–0.895) | <0.001 | 1.18 (1.06–1.305) | 0.93 (0.89–0.97) | 0.002 |
Cool body temperature | 0.99 (0.947–1.045) | 1.012 (0.903–1.135) | 0.8 | 1.00 (0.895–1.13) | 0.99 (0.95–1.05) | 0.9 |
Weight gain | 1.18 (1.12–1.23) | 0.62 (0.522–0.733) | <0.001 | 1.27 (1.13–1.44) | 0.89 (0.835–0.95) | <0.001 |
Low energy | 1.35 (1.18–1.548) | 0.89 (0.855–0.935) | <0.001 | 1.05 (1.01–1.106) | 0.89 (0.794–0.999) | 0.05 |
Nested case–control study
Baseline characteristics
Biomarker changes
Serum parameter | Case | Control | Between groups comparison (P-value)a
| ||||
---|---|---|---|---|---|---|---|
N
| Baseline (mean ± SD | Follow-up (mean ± SD) |
N
| Baseline (mean ± SD) | Follow-up (mean ± SD) | ||
FT3 (pmol/L) | 103 | 4.34 ± 0.6 | 4.57 ± 0.2b
| 412 | 4.85 ± 0.7 | 4.30 ± 0.5b
| <0.001 |
FT4 (pmol/L) | 103 | 9.06 ± 1.1 | 13.4 ± 1.0b
| 412 | 14.7 ± 2.8 | 13.5 ± 1.0b
| <0.001 |
Anti-TPO (kU/L) | 103 | 162.8 ± 120 | 43.4 ± 116b
| 412 | 21.5 ± 54.8 | 18.8 ± 26.7 | <0.001 |
Anti-TG (kU/L) | 103 | 51.8 ± 33.7 | 17.6 ± 27.2b
| 412 | 32.0 ± 61.3 | 14.5 ± 30.7b
| 0.05 |
TSH (mlU/L) | 103 | 5.97 ± 4.2 | 2.50 ± 1.1b
| 412 | 1.78 ± 0.7 | 1.98 ± 0.6b
| <0.001 |
TG (µg/L) | 31 | 43.1 ± 39.4 | 25.6 ± 4.0b
| 244 | 28.2 ± 26.3 | 25.4 ± 5.9 | 0.003 |
hs-CRP (mg/L) | 103 | 2.05 ± 2.2 | 2.52 ± 1.4 | 412 | 2.35 ± 3.1 | 2.41 ± 1.9 | 0.2 |
25(OH)D (nmol/L) | 103 | 68 ± 32 | 110 ± 14b
| 412 | 82 ± 34 | 110 ± 27b
| 0.001 |
Vitamin D dose (IU/day) | 103 | 1243 ± 2606 | 3517 ± 2620b
| 412 | 1824 ± 2770 | 4150 ± 3321b
| 0.9 |