Relationship between high normal TSH levels and metabolic syndrome components in type 2 diabetic subjects with euthyroidism

Abstract

a b s t r a c tObjective: Thyroid hormones as modulators of adaptive thermogenesis can potentially contribute to development of obesity. The purpose of our study is to observe a relationship between TSH and BMI, blood lipids, BP and HbA1c in type 2 diabetic subjects with euthyroidism. Methods: A total of 120 subjects with type 2 diabetes were recruited for this study from November 2012 to June 2014. Subjects were included in the study with TSH values between 0.4 and 4.5 mU/l, who did not take any thyroid medication and had a similar iodine diet. Subjects were weighed and anthropometric indices, lipid parameters, fasting plasma glucose, HbA1c, eGFR, blood pressure (BP) were documented. TSH was measured by an electrochemiluminescence immunoassay. Statistical analysis was performed by using SPSS 18(P value <0.05 was considered significant). Results: The mean age of the participants was 60.6 AE 11.6 years with a BMI of 25.3 AE 3.1 kg/m 2 . Serum TSH levels were significantly and positively associated with BMI, systolic and diastolic BP, serum triglyceride and HbA1c levels, whereas negatively with eGFR. Subjects with a TSH in a higher normal range (2.5e4.5 mU/I, n ¼ 58) had a significantly higher BMI (26.7 AE 3 vs. 24.1 AE 2.7) and this relation remained significant adjusted for age and sex (P < 0.001). When TSH was in low normal range, the number of patients with glycemic goal (HbA1c > 7%) decreased from 27.5% to 12.5% (P ¼ 0.02, adjusted for age and sex). Conclusion: In type 2 diabetic subjects with biochemical euthyroidism we found significant association between high normal TSH levels and components of metabolic syndrome. High normal TSH levels were associated with more number of subjects with glycemic goal (HbA1c >7%).

The role of thyroid hormone in metabolism and metabolic syndrome

“…As demonstrated in Table 2, glycemia or glycosylated hemoglobin might be positively 37,46,62,75,93,94,100,153 or negatively 33,66,76 associated with serum TSH levels. A positive association between TSH levels (or reduced thyroid function) and abnormal glucose metabolism may be related to the importance of the action of TH in different pathways related to glucose transport, especially those related to the expression of GLUT 4, as previously described.…”

“…However, the NCEPT/ATPIII was the most commonly applied criteria for diagnosis. 14,16,19,25,26,38,48,54,68,69,73,77,92,94,97,98,102 Other authors used the IDF criteria, 42,47,55,56,75,81,93 the World Health Organization or American Heart Association criteria, 45,62,79 or even local/regional or pre-established criteria defined by a joint interim statement. 29,45,52,76,96 Finally, some studies defined MetS by the presence of IR according to an abnormal Homeostatic Model Assessment of Insulin Resistance index (HOMA-IR) or euglycemic clamp result.…”

“…8–14 Sectional studies have shown that the overlap between both diagnoses is common, justifying a high association between them, as shown in Table 2. 14,15…”

The thyroid hormone levels and glucose and lipid metabolism in children with type 1 diabetes: a correlation analysis

“…it's been found in T2DM female patients with normal thyroid function, TSH is positively correlated with TC and LDL-C, but it has no significant correlation with TG and HDL-C, but in male patients, TSH and TC, TG, LDL-C and HDL-C have no obvious correlation (24). Besides, it has found that in T2DM patients with normal thyroid function, TSH was positively correlated with TG and HbAlc (25), and it has no significant correlation with FBG, LDL-C and HDL-C, while FT3 and FT4 had no significant relations to glucose and lipid metabolism (26). Previous studies (27)(28)(29) have indicated that in T2DM patients, thyroid hormone levels are closely related to glucose and lipid metabolism, but there are few studies on the relationship between thyroid hormone levels and glucose and lipid metabolism in T1DM patients, especially in TIDM children with normal thyroid function.…”