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

Abstract

ObjectiveThyroid 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.MethodsA 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).ResultsThe mean age of the participants was 60.6 ± 11.6 years with a BMI of 25.3 ± 3.1 kg/m2. 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 (2.5–4.5 mU/I, n = 58) had a significantly higher BMI (26.7 ± 3 vs. 24.1 ± 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 = 0.02, adjusted for age and sex).ConclusionIn 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%).

Association between Thyroid Hormone Levels and Diabetic Kidney Disease in Euthyroid Patients with Type 2 Diabetes

“…Meanwhile, the National Academy of Clinical Biochemistry (NACB) recommended lowering the upper reference limit of TSH to 2.5 uIU/mL based on a large-scale epidemiological survey in 2003, which stated that >95% of the normal individuals presented TSH levels <2.5 uIU/mL, and those with high TSH levels were likely to experience various thyroid disorders 15 . In addition, several similar investigations 7 , 16 , 17 divided the participants within the normal range of TSH into TSH <2.5μIU/mL and TSH ≥2.5 μIU/mL groups. Thus, we divided the subjects into 2 groups according to TSH <2.5μIU/mL and TSH ≥2.5 μIU/mL.…”

Effect of rhTSH on Lipids

“…The hypothesis that TSH can directly increase the lipids level is relatively recent, and based on associated studies not only in patients with increased TSH level (e.g., subclinical/overt hypothyroidism), but also in subjects with TSH within the normal reference range [16]. Indeed, TSH can contribute to increase LDLc by increasing the Proprotein convertase subtilisin/kexin type 9 (PCSK9) [17].…”

Screening of Undiagnosed Hypothyroidism in Elderly Persons with Diabetes according to Age-Specific Reference Intervals for Serum Thyroid Stimulating Hormone and the Impact of Antidiabetes Drugs

“…We postulate that this may be due to selection bias because this group also had the highest BMI and HbA1c levels. Previous studies showed a positive correlation between TSH, even within its normal range, and body weight/BMI and HbA1c [ 12 , 40 – 42 ]. One study linked increased weight with the susceptibility to harbor thyroid autoimmunity [ 43 ].…”