The purpose of this study was to determine thiobarbituric acid-reactive substance (TBARS) levels in subclinical hypothyroidism and to examine the effect of levothyroxine replacement on TBARS levels. A cohort of 28 female patients with subclinical hypothyroidism and 24 healthy controls were enrolled in this study. The levels of plasma TBARS, serum lipids, and high-sensitive C-reactive protein (CRP) in patients with subclinical hypothyroidism at baseline and after achieving euthyroid state by levothyroxine were assessed. TBARS levels of the patients were similar to those of the control group in the subclinical hypothyroid state and after restoration of euthyroidism by levothyroxine replacement. TBARS levels decreased after levothyroxine treatment, but did not reach statistical significance. There was no significant correlation between TBARS, lipid and CRP levels. Serum CRP levels were higher in subclinical hypothyroidism (4.28 +/- 0.9 mg/l) than in the control group (1.95 +/- 0.34 mg/l) and the difference was statistically significant (p = 0.03). After achieving euthyroid state, CRP levels decreased significantly in patients with subclinical hypothyroidism from 4.28 +/- 0.9 to 2.32 +/- 0.6 mg/l (p = 0.006). Our findings suggest that there is no significant alteration of plasma TBARS levels neither in subclinical hypothyroid state nor after achieving euthyroid state. Serum CRP level is higher in patients with subclinical hypothyroidism than in the control group. Normalization of thyroid state seems to effectively reduce serum CRP levels in subclinical hypothyroidism without any correlation with TBARS activity. Copyright 2007 S. Karger AG, Basel.
