Abstract
Background: Subclinical hypothyroidism (SCH) is defined as raised serum TSH levels with circulating thyroid hormones within the reference range. It is uncertain whether treatment of SCH with L-thyroxine improves cardiovascular (CV) risk factors.
Objective: To evaluate the therapeutic effect of L-thyroxine in lipid profile, CRP (C-reactive protein) and homocysteine levels in SCH caused by autoimmune thyroiditis (AIT).
Patients and methods: We recorded total cholesterol (TC), HDL and LDL-cholesterol, triglycerides (TG), apolipoprotein B (ApoB), ApoA1, lipoprotein (a) (Lp[a]), homocysteine, CRP, folic acid and vitamin B12 levels, before and 6 months after starting treatment with L-thyroxine in 120 patients (mean age 45.7 ± 12.2 yr, 80 females, mean BMI 28.35 ± 0.8 Kg/m2) with SCH (mean TSH 6.429 ± 0.534 mIU/liter) not previously treated for thyroid or vascular disease. Statistical analysis was performed with Students t-test.
Results: are expressed as means ± SD. A two-tailed p value < 0.05 was considered significant. Results -There were no significant differences between folic acid, vitamin B12, homocysteine, CRP, and TG levels before and after L-thyroxine treatment. TC and LDL levels significantly decreased (199.29 ± 20.39 mg/dl vs 152.25 ± 19.12 mg/dl, p< 0.01; 116.12 ± 34.23 mg/dl vs 91.22 ±16.25 mg/dl, p< 0.01, respectively). Apo B levels also significantly decreased with L-thyroxine treatment (128.32 ± 44.11mg/dl vs 97.84 ± 29.31mg/dl, p< 0.01). Lp(a) levels were significantly lower after L-thyroxine treatment (31.96mg/dl ±19.11mg/dl vs 21.42 ± 18.12mg/dl, p< 0.01). HDL and Apo A1 levels increased significantly after L-thyroxine treatment (45.18 ± 15.29mg/dl vs 58.47 ± 18.10mg/dl, p< 0.01; 124.48 ± 43.26mg/dl vs 136.52 ± 56.39mg/dl, p< 0.01, respectively).
Conclusions: Autoimmune SCH treated with L-thyroxine leads to significant improvement in CV risk factors.