Abstract
BackgroundThe concept is now emerging that higher thyroid-stimulating hormone (TSH) and lower thyroid hormone levels within the euthyroid range may adversely affect atherosclerosis. The aim of this study was to investigate the potential association between thyroid parameters and lipids profile in a cohort of euthyroid diabetic subjects.MethodsFour hundred and sixty-two euthyroid type 2 diabetes subjects (302 males and 160 females) were consecutively recruited. Clinical and anthropometric data was collected from all participants. Whole blood samples were drawn in the morning after an overnight fasting for the measurement of serum TSH, free thyroxine (FT4), free triiothyronine (FT3), anti-thyroid peroxidase antibody (TPO-Ab) levels, as well as lipid concentrations and glucose.ResultsTSH was higher in females than males. Stratified by TSH, high-density lipoprotein cholesterol (HDL-c) level increased in subjects with TSH ≥2.5uIU/mL (P = 0.004). And TSH was associated with HDL-c in a Pearson correlation test, however, the association failed to attain significance in partial correlation analyses, adjusted for age, sex, duration of diabetes, fasting glucose and BMI. In females, total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-c) level was significant lower in subjects with TSH <2.5uIU/mL. TSH was significantly associated with TC and LDL-c, even in a partial correlation analysis (P = 0.006 and 0.011, respectively). In a multiple linear regression analysis (stepwise), TSH was positive associated with TC (β = 0.202, P = 0.005) and LDL-c (β = 0.144, P = 0.010). In one hundred and six patients having TPO antibody assays, 6 (5.66%) were positive. The blood pressure and lipid levels were lower in TPO-Ab positive patients, however, the differences were not significantly.ConclusionsIn conclusion, we identified TSH was positively associated with serum TC and LDL-c in euthyroid diabetic women. Our analysis in the subgroup having TPO antibody assays demonstrating non-significantly lower TC levels among seropositive subjects was consistent with the above stated consideration for women as a whole. Further investigations are needed to understand the intimate mechanisms of lipid metabolism in type 2 diabetes with respect to thyroid function.
Highlights
The concept is emerging that higher thyroid-stimulating hormone (TSH) and lower thyroid hormone levels within the euthyroid range may adversely affect atherosclerosis
Age and TSH level were higher in females, and body mass index (BMI), diastolic blood pressure (DBP), and Free triiodothyronine (FT3) were lower
Stratified by TSH, high-density lipoprotein cholesterol (HDL-c) level increased in subjects with TSH ≥2.5uIU/mL (P = 0.004, Table 1)
Summary
The concept is emerging that higher thyroid-stimulating hormone (TSH) and lower thyroid hormone levels within the euthyroid range may adversely affect atherosclerosis. Hypothyroidism had been reported to be associated with an increased risk for dyslipidemia and atherosclerotic cardiovascular disease [1,2]. The concept was Diabetes mellitus, in particular type 2 diabetes, which was mostly associated with lipoid abnormalities [5], was known to dramatically increased risk of cardiovascular diseases [6]. The association between circulating TSH levels and cardiovascular diseases risk factors seemed to be amplified by the degree of insulin-resistance [8], and it might be relevant in type 2 diabetes. Several studies had reported that even relative low thyroid functions that were still within normal range were more frequent and might be more dangerous in people with diabetes [9,10,11]. In most of these studies, free triiodothyronine (FT3), free thyroxine (FT4) and TSH were not measured together
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