Purpose: Although the relationship between atherosclerosis and overt hypothyroidism has been confirmed, it remains controversial in cases of subclinical hypothyroidism. Higher TSH and similar T4 suggest differences in set-points or differences due to diagnostic limitations regarding subclinical hypothyroidism. Endothelial dysfunction (ED) is a marker rather than a precursor of cardiovascular disease. Asymmetric dimethylarginine (ADMA) and endocan are known as novel markers of ED in various diseases. Transforming growth factor-beta (TGF-β) has a protective role against autoimmune diseases such as thyroiditis. This study aimed to determine the relationships between serum ADMA, endocan, TGF-β, and the high-sensitivity C-reactive protein (hs-CRP) levels, a proven indicator of ED, in patients with SH.
Methods: Thirty-five patients with SH and 21 age- and sex-matched euthyroid subjects were included in the study. The levels of TSH, FT4, lipid parameters, endocan, ADMA, TGF-β, and hs-CRP were measured.
Results: No significant differences in age or sex were found between the patient and control groups (p=0.294 and 0.881, respectively). Mean TSH level was higher in the patient group (p=0.005), whereas mean fT4 level was similar in two groups (p=0.455). The average hs-CRP, endocan, TGF-β l level in the patient group was higher than control group (p=0.001; P=0.012; P=0.025; P<0.01 respectively). A positive correlation was found between the endocan and ADMA levels (r=0.760, p=0.000). ADMA levels also were positively correlated with hs-CRP. Both the TSH and low-density lipoprotein cholesterol (LDL-C) levels were positively correlated with the hs-CRP level.
Conclusions: Subclinical hypothyroidism is associated with increased levels of serum endocan, ADMA, and TGF-β, which are new markers for ED. In particular, ADMA was correlated with both endocan and hs-CRP levels. These findings are suggestive for increased risk of ED and subsequent development of atherosclerosis in patients with SH.
Keywords: ADMA; Endocan; Subclinical Hypothyroidism; TGF-beta.
© 2016 by the Association of Clinical Scientists, Inc.