Clinical Associations of Thyroid Hormone Levels with the Risk of Atherosclerosis in Euthyroid Type 2 Diabetic Patients in Central China

Abstract

<jats:p><jats:italic>Background</jats:italic>. Thyroid function is associated with the etiology and pathogenesis of type 2 diabetes (T2D) and potentially contributes to the development of the complications of T2D. The association of thyroid hormones with atherosclerosis in euthyroid T2D patients is not clear. <jats:italic>Purpose</jats:italic>. To investigate the association of thyroid hormone levels with the risk of developing atherosclerosis in euthyroid T2D patients in Central China. <jats:italic>Methods</jats:italic>. This cross-sectional study recruited 910 euthyroid T2D patients from Henan Provincial People’s Hospital, China. Association among hemoglobin A1c (HbA1c), thyroid hormones, and the prevalence of atherosclerosis was assessed by multivariable Cox models after adjusting for covariates including age, BMI, duration of T2D, smoking status, SBP, TC, family history of T2D, and medications on hyperlipidemia. <jats:italic>Results</jats:italic>. Among all 910 subjects, 373 were diagnosed with atherosclerosis. There were 523 females and 387 males included in this study. The mean age was 51.9 years. The average BMI was 25.3 kg/m<jats:sup>2</jats:sup>. Low-normal serum-free triiodothyronine (FT3) levels (3.50–4.17 pmol/L) were associated with a high prevalence of atherosclerosis. Comparing with low-normal FT3, the prevalence ratio in patients with mid- (4.17–4.83 pmol/L) and high-normal FT3 level (4.83–6.50 pmol/L) is 0.74 (95% CI 0.56 to 0.97, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mi>p</mml:mi><mml:mo>=</mml:mo><mml:mn>0.029</mml:mn></mml:math>) and 0.63 (95% CI 0.46 to 0.87, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mi>p</mml:mi><mml:mo>=</mml:mo><mml:mn>0.005</mml:mn></mml:math>) after adjusting for covariates. High level of free thyroxine (FT4) also had decreased risk for atherosclerosis. Thyroid-stimulating hormone (TSH) and FT3 to FT4 ratio did not show significant association with the development of atherosclerosis. <jats:italic>Conclusion</jats:italic>. T2D patients with low but clinically normal FT3 level are more likely to develop macrovascular complications comparing with those with mid- and high-normal FT3 level.</jats:p>

Serum free triiodothyronine is inversely associated with diabetic peripheral neuropathy but not with carotid atherosclerotic lesions in euthyroid patients with type 2 diabetes

“…This discrepancy can be explained by the fact that the different definitions of macrovascular complications were used in above studies. That is, the macrovascular complications in the studies by Wang et al [ 38 ] and Hu et al [ 12 ] were defined as atherosclerosis from the aorta, coronary, basilar and carotid, while our current study mainly focused on carotid atherosclerotic lesions.…”

“…However, studies regarding the associations between FT3 levels and macrovascular complications in euthyroid patients with type 2 diabetes are quite few. Recently, a study by Wang et al [ 38 ] displayed that diabetic patients with low-normal FT3 level were more likely to suffer from macrovascular complications than those with mid-and-high normal FT3 level. Hu et al [ 12 ] also revealed that there was a remarkable relation between diabetic macrovascular complications and normal FT3 (OR = 0.534, 95% CI 0.358–0.796).…”

Associations of Thyroid Hormone Levels and Macrovascular Complications in Euthyroid Type 2 Diabetic Patients

“…Since BMI could influence the association between thyroid hormones and diabetes complications, we calculated the stratum-specific ORs for normal or underweight patients (BMI<25) and overweight or obese patients (BMI≥25) to test the effect modification by BMI. Based on the correlations between HbA1c and the development of atherosclerosis in T2DM patients demonstrated in previous researches, 13 patients with normal HbA1c (<6.0%) were rarely encountered in our study (only 26 patients). Hence, we performed sensitivity analyses by excluding patients with normal HbA1c.…”

“…However, a case-control study conducted in China suggested that low-normal FT3 and FT4 levels contributed to a high prevalence of atherosclerosis after adjusting for covariates. 13 However, TSH and FT3 to FT4 ratio did not show any significant association with the development of atherosclerosis. Moreover, they analyzed the association of thyroid function with HbA1c and the association of HbA1c with the prevalence of atherosclerosis.…”

Serum Free Triiodothyronine Is Inversely Associated With Diabetic Peripheral Neuropathy but Not With Carotid Atherosclerotic Lesions in Type 2 Diabetic Patients With Euthyroid Function

“…Lately, some scholars further explored the associations of FT3 Levels and macrovascular complications in type 2 diabetic patients with normal thyroid function [42,43]. Different from us, Wang et al [42] showed that diabetic patients with low-normal FT3 level were more likely to suffer from macrovascular complications than those with mid-and-high normal FT3 level. Hu et al [43] also revealed that there was a remarkable relationship between diabetic macrovascular complications and normal FT3 (OR = 0.534, 95% CI 0.358-0.796).…”