Fig. 1Flow chart of the study population.
Table 1Baseline Characteristics of Study Subjects
Variable |
Metabolic syndrome |
Overall (n=13,496) |
No (n=11,832) |
Yes (n=1,664) |
P value |
Male sex |
6,852 (58) |
1,316 (79) |
<0.001 |
8,168 (61) |
Age, yr |
50.5±6.6 |
52.3±6.5 |
<0.001 |
50.7±6.6 |
Smoking, current/former/never, % |
17/29/54 |
27/37/36 |
<0.001 |
19/30/51 |
BMI, kg/m2
|
23.4±2.6 |
26.5±2.4 |
<0.001 |
23.8±2.7 |
Overweight (25≤BMI<30) |
2,784 (24) |
1,258 (76) |
<0.001 |
4,042 (30) |
Obesity (BMI≥30) |
134 (1) |
109 (7) |
<0.001 |
243 (2) |
Body fat, % |
23.3±6.1 |
25.7±5.7 |
0.004 |
23.6±6.1 |
Male |
20.2±4.4 |
23.8±4.1 |
<0.001 |
20.8±4.5 |
Female |
27.7±5.4 |
33.1±4.9 |
<0.001 |
28.0±5.5 |
Abdominal fat, % |
0.88±0.06 |
0.93±0.06 |
<0.001 |
0.88±0.06 |
Male |
0.89±0.06 |
0.93±0.05 |
<0.001 |
0.90±0.06 |
Female |
0.85±0.06 |
0.91±0.06 |
<0.001 |
0.86±0.06 |
Systolic BP, mm Hg |
109.9±14.2 |
121.0±15.3 |
<0.001 |
111.3±14.8 |
Diastolic BP, mm Hg |
67.7±9.8 |
74.4±10.0 |
<0.001 |
68.5±10.0 |
Total cholesterol, mg/dL |
188.0±30.7 |
191.9±33.2 |
<0.001 |
188.5±31.0 |
LDL-C, mg/dL |
122.8±27.9 |
125.4±29.9 |
0.001 |
123.1±28.2 |
HDL-C, mg/dL |
59.4±13.5 |
47.3±10.9 |
<0.001 |
57.9±13.8 |
Male |
55.5±11.9 |
47.2±11.3 |
<0.001 |
54.2±12.2 |
Female |
64.8±13.8 |
47.7±9.2 |
<0.001 |
63.6±14.2 |
Triglycerides, mg/dL |
114.7±63.9 |
214.0±102.5 |
<0.001 |
126.9±77.1 |
Fasting glucose, mg/dL |
87.5±12.9 |
103.7±23.8 |
<0.001 |
89.5±15.6 |
HbA1c, % |
5.3±0.5 |
5.9±0.9 |
<0.001 |
5.4±0.6 |
HOMA-IR |
1.9±0.9 |
2.9±1.5 |
<0.001 |
2.1±1.1 |
TSH, mU/L |
2.4±1.3 |
2.3±1.3 |
0.017 |
2.3±1.3 |
T3, nmol/L |
1.72±0.28 |
1.78±0.29 |
<0.001 |
1.72±0.28 |
T4, nmol/L |
108.6±17.9 |
108.3±18.4 |
0.521 |
108.6±17.9 |
T3-to-T4 ratio |
0.016±0.003 |
0.017±0.003 |
<0.001 |
0.016±0.003 |
Table 2Means for Thyroid Hormone Levels by Select Metabolic Syndrome Components
Variable |
No. (%) |
Thyroid hormones |
TSH, mU/L |
T3, nmol/L |
T4, nmol/L |
T3-to-T4 ratio |
BMI, kg/m2
|
|
|
|
|
|
Underweight (<18.5) |
219 (2) |
2.6±1.3a,*
|
1.67±0.28a,*
|
109.7±17.4a,‡
|
0.015±0.003a,*
|
Normal (18.5-24.9) |
8,992 (66) |
2.4±1.3a,*
|
1.71±0.28b,*
|
108.8±17.9a,‡
|
0.016±0.003b,*
|
Overweight (25-29.9) |
4,042 (30) |
2.2±1.2b,*
|
1.75±0.28c,*
|
108.0±17.9b,‡
|
0.017±0.003c,*
|
Obesity (≥30) |
243 (2) |
2.2±1.2b,*
|
1.79±0.26d,*
|
110.9±20.0c,‡
|
0.017±0.003c,*
|
Systolic BP, mm Hg |
|
|
|
|
|
<130 |
10,272 (76) |
2.3±1.3 |
1.71±0.28*
|
108.3±17.8*
|
0.016±0.003†
|
≥130e
|
3,224 (24) |
2.3±1.3 |
1.76±0.29*
|
109.7±18.3*
|
0.017±0.003†
|
Diastolic BP, mm Hg |
|
|
|
|
|
<85 |
10,756 (80) |
2.3±1.3 |
1.71±0.28*
|
108.3±17.8*
|
0.016±0.003‡
|
≥85e
|
2,739 (20) |
2.3±1.3 |
1.76±0.29*
|
109.9±18.5*
|
0.017±0.003‡
|
HDL-C, mg/dL |
|
|
|
|
|
Lowf
|
1,555 (12) |
2.5±1.3*
|
1.68±0.28* |
108.8±17.7 |
0.016±0.003*
|
Highg
|
11,941 (88) |
2.3±1.3*
|
1.73±0.28* |
108.6±17.9 |
0.017±0.003*
|
Triglycerides, mg/dL |
|
|
|
|
|
<150 |
9,966 (74) |
2.3±1.3 |
1.70±0.28*
|
108.8±17.9 |
0.016±0.003*
|
≥150 |
3,530 (26) |
2.4±1.3 |
1.80±0.28*
|
108.1±18.1 |
0.017±0.003*
|
Fasting glucose, mg/dL |
|
|
|
|
|
<100 |
11,484 (85) |
2.4±1.3*
|
1.72±0.28*
|
108.6±17.8 |
0.016±0.003*
|
≥100h
|
2,012 (15) |
2.2±1.2*
|
1.75±0.29*
|
108.6±18.6 |
0.017±0.003*
|
HbA1c, % |
|
|
|
|
|
<5.7 |
10,636 (79) |
2.4±1.3a,‡
|
1.72±0.28a,*
|
108.5±17.8a,†
|
0.016±0.003a,*
|
5.7-6.4 |
1,992 (15) |
2.3±1.3a,b,‡
|
1.75±0.29b,*
|
108.6±17.8a,†
|
0.017±0.003b,*
|
≥6.5h
|
868 (6) |
2.2±1.3b,‡
|
1.73±0.30a,*
|
110.4±19.6b,†
|
0.016±0.003a,*
|
Table 3Risk of Metabolic Syndrome in Euthyroid Subjects according to Thyroid Hormone Quartiles
Thyroid hormone category |
Metabolic syndrome/total, n (%) |
OR (95% CI) |
Model 1 |
Model 2 |
Model 3 |
TSH quartiles, mU/L |
|
|
|
|
0.4-1.4 |
481/3,744 (13) |
1 |
1 |
1 |
1.5-2.1 |
395/3,414 (12) |
0.888 (0.747-1.055) |
0.919 (0.772-1.095) |
0.926 (0.727-1.178) |
2.2-3.0 |
423/3,085 (14) |
1.078 (0.909-1.279) |
1.170 (0.983-1.391) |
1.245 (0.982-1.577) |
3.1-5.0 |
365/3,253 (11) |
0.857 (0.719-1.023) |
1.016 (0.848-1.217) |
1.134 (0.887-1.452) |
T3 quartiles, nmol/L |
|
|
|
|
1.10-1.51 |
323/3,307 (10) |
1 |
1 |
1 |
1.52-1.69 |
403/3,373 (12) |
1.254 (1.074-1.464)†
|
1.217 (1.040-1.424)‡
|
1.025 (0.829-1.268) |
1.70-1.89 |
415/3,470 (12) |
1.255 (1.076-1.464)†
|
1.169 (1.001-1.366)‡
|
1.000 (0.809-1.235) |
1.90-2.90 |
523/3,346 (16) |
1.712 (1.476-1.984)*
|
1.570 (1.351-1.824)*
|
1.249 (1.020-1.529)†
|
T4 quartiles, nmol/L |
|
|
|
|
64.0-96.0 |
481/3,631 (13) |
1 |
1 |
1 |
96.1-107.0 |
390/3,387 (12) |
0.852 (0.716-1.014) |
0.870 (0.730-1.038) |
0.867 (0.685-1.097) |
107.1-119.5 |
354/3,153 (11) |
0.828 (0.693-0.990)† |
0.814 (0.680-0.975)†
|
0.746 (0.582-0.956)†
|
119.6-155.0 |
439/3,325 (13) |
0.996 (0.841-1.180) |
0.942 (0.794-1.119) |
0.890 (0.706-1.121) |
T3-to-T4 ratio quartiles |
|
|
|
|
0.0060-0.0140 |
333/3,379 (10) |
1 |
1 |
1 |
0.0141-0.0159 |
375/3,406 (11) |
1.132 (0.936-1.368) |
1.132 (0.934-1.371) |
1.097 (0.843-1.428) |
0.0160-0.0179 |
428/3,329 (13) |
1.350 (1.122-1.624)*
|
1.358 (1.126-1.638)*
|
1.275 (0.988-1.646) |
0.0180-0.0565 |
528/3,382 (16) |
1.692 (1.416-2.022)*
|
1.616 (1.349-1.936)*
|
1.458 (1.141-1.863)*
|