TSH and free thyroxine concentrations are associated with differing metabolic markers in euthyroid subjects.
OBJECTIVE
To examine the association between thyroid function and the components of the metabolic syndrome and insulin resistance in an Hispanic population.


METHODS
Cross-sectional study.


METHODS
Subjects with no history of thyroid disease or diabetes were included. Thyroid function was stratified as euthyroid or subclinical hypothyroidism (SCH) status and subsequently by free thyroxine (FT(4)) and TSH tertiles. The association of the metabolic syndrome components (defined by 2004 Adult Treatment Panel III criteria) and insulin resistance with thyroid status, TSH, and FT(4) were examined.


RESULTS
A total of 3148 subjects were analyzed. The prevalence of SCH was 8.3%. The prevalence of the metabolic syndrome was similar in euthyroid and SCH patients (31.6 vs 32.06%, P=0.89). Total cholesterol was higher in patients with SCH (5.51+/-1.19 vs 5.34+/-1.05 mmol/l, P<0.032). Serum TSH values showed a positive correlation (adjusted for age and sex) with total cholesterol, triglycerides, and waist circumference. In contrast, FT(4) showed a positive correlation with high-density lipoprotein cholesterol, and an inverse correlation with waist circumference, insulin, and HOMA-IR.


CONCLUSIONS
SCH is not associated with an increased risk for the metabolic syndrome (as conceived as a diagnostic category defined by the National Cholesterol, Education Program, Adult Treatment Panel III criteria). Despite this, low thyroid function (even in the euthyroid state) predisposes to higher cholesterol, glucose, insulin, and HOMA-IR levels. The combined use of TSH and FT(4), compared with the assessment based on only FT(4), is a more convenient approach to evaluate the association between thyroid function and metabolic variables.
Departamento de Endocrinologia y Metabolismo, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, Mexico City, Mexico.
Jose de Jesus
Jde J
Garduño-Garcia
Ulices
U
Alvirde-Garcia
Guadalupe
G
López-Carrasco
Ma Elena
ME
Padilla Mendoza
Roopa
R
Mehta
Olimpia
O
Arellano-Campos
Ricardo
R
Choza
Leobardo
L
Sauque
Maria Eugenia
ME
Garay-Sevilla
Juan Manuel
JM
Malacara
Francisco J
FJ
Gomez-Perez
Carlos A
CA
Aguilar-Salinas
D015415:Biomarkers; D001786:Blood Glucose; D008076:Cholesterol, HDL / Q000097:blood; D003430:Cross-Sectional Studies; D005260:Female; D006630:Hispanic or Latino; D006801:Humans; D007037:Hypothyroidism / Q000097:blood* / Q000453:epidemiology*; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008297:Male; D024821:Metabolic Syndrome / Q000097:blood / Q000453:epidemiology*; D008800:Mexico; D015995:Prevalence; D012307:Risk Factors; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000378:metabolism; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood; D055105:Waist Circumference
D015415:Biomarkers; D001786:Blood Glucose; D008076:Cholesterol, HDL; D007328:Insulin; D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine