TSH and free thyroxine concentrations are associated with differing metabolic markers in euthyroid subjects

Abstract

Objective: To examine the association between thyroid function and the components of the metabolic syndrome and insulin resistance in an Hispanic population. Design: 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%, PZ0.89). Total cholesterol was higher in patients with SCH (5.51G1.19 vs 5.34G1.05 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. Conclusion: 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.

Fatty liver largely explains associations of subclinical hypothyroidism with insulin resistance, metabolic syndrome, and subclinical coronary atherosclerosis

“…SCH subjects have been shown to have similar (13), higher (7,8), or lower (12) insulin and HOMA-IR levels, compared with euthyroid control subjects. Similarly, Garduño-Garcia et al (13) found that the prevalence of MS was not different between SCH subjects and individuals with normal thyroid function, while another study demonstrated that the syndrome was significantly more prevalent in subjects with both overt thyroid failure and SCH than in euthyroid subjects (9). Interestingly, a very recent study conducted in overweight and obese children has demonstrated a multivariate-adjusted association of SCH with insulin resistance and MS (7).…”

“…Although some studies have reported associations of SCH with insulin resistance (7,8), metabolic syndrome (MS) (7,9), and CHD (10,11), not all previous findings have been consistent (12,13,14). Recent studies in adults (9,15,16) and children (7) have shown that SCH is closely associated with NAFLD independent of potential confounders.…”

The association of autoimmune thyroiditis and non-functional adrenal incidentalomas with insulin resistance

“…Garduño-Garcia and cols. reported a significant association between fT4 levels and high-density lipoprotein cholesterol, insulin and HOMA-IR (10).…”

Serum vaspin levels in hypothyroid patients

“…The association between serum TSH and the components of metabolic syndrome varied in different studies. In some recent studies, thyroid dysfunction (23) and even TSH within the normal range (19,24,25) were reported to be associated with insulin resistance and components of metabolic syndrome. By contrast, some other studies failed to detect a significant association between TSH and insulin resistance (19,21,22,26).…”