Levothyroxine therapy reduces endocan and total cholesterol concentrations in patients with subclinical hypothyroidism.

Introduction: Subclinical hypothyroidism (SCH) is an independent risk factor for cardiovascular diseases due to endothelial dysfunction and atherosclerosis development. The aim of this study was to determine whether the levothyroxine therapy could impact the concentrations of endothelial dysfunction blood markers, namely endothelin-1 (ET-1), asymmetric dimethylarginine (ADMA) and endocan, in patients with a mild form of SCH (thyroid-stimulating hormone (TSH) ≤ 10 mIU/L).

Materials and methods: In this case-control prospective study, SCH patients and healthy controls were recruited during their regular health examinations. Medical specialists prescribed levothyroxine to SCH patients if necessary. The endothelial dysfunction markers, as well as other biochemical markers, were measured in all subjects at baseline, and after 6 months of levothyroxine treatment following the euthyroidism.

Results: Our study showed higher ADMA (248.00 (168.78-540.20) vs. 166.30 (140.60-243.40) μg/L, P = 0.002), endocan (114.30 (63.45-194.65) vs. 67.26 (50.80-126.10) ng/L, P = 0.004), low-density lipoprotein cholesterol (LDL) (3.3 ± 0.6 vs. 3.7 ± 0.9 mmol/L, P = 0.043) and non-high-density lipoprotein cholesterol (non-HDL) (3.8 ± 0.7 vs. 4.2 ± 1.0 mmol/L, P = 0.020) concentrations in patients with a mild form of SCH in comparison with healthy subjects. In SCH patients, after 6 months of levothyroxine treatment following the euthyroidism, we observed a significant decrease in endocan (91.47 (61.88-200.03) vs. 97.90 (55.18-154.88) ng/L, P = 0.004), and total cholesterol concentrations (CHOL) (6.2 ± 1.0 vs. 5.8 ± 1.0 mmol/L, P = 0.039).

Conclusions: A mild form of SCH is associated with higher concentrations of endocan, ADMA, LDL and non-HDL. The potential benefits of levothyroxine therapy were shown through the significant decrease of endocan and CHOL concentrations in SCH patients, thus contributing the atherosclerosis prevention.