The effect of thyroid hormone replacement therapy on arterial stiffness in subclinical hypothyroidism

Arterial stiffness increases in subclinic hypothyroidism. It is alreadyknown that arterial stiffness increases in the early period of atherosclerosis.In this study, our aim was to determine whether thyroid hormone replacementdecreases the arterial stiffness in subclinic hypothyroidism.This study was performed with the patients who applied to Cardiologyand Internal Medicine Clinics of Afyonkarahisar Kocatepe University, Schoolof Medicine, Ahmet Necdet Sezer Teaching and Education Hospital, between2007 February and 2008 June. Forty-one patients, who had recentlydiagnosis of subclinic hypothyroidism, were included into the study. Meanage of the patients was 39.34±9.6 (ranging between 19 and 50 years) and 34(83%) of them were female and 7 (17%) of them were male. Patients whohad diagnosis of diseases resulting in endothelial dysfunction such asdiabetes mellitus, hypertension, coronary artery disease, heart failure,chronic renal failure were excluded fom the study. Patients were examinedwith Trace 6000 Modul (Micro Medical, Rochester, United Kingdom), adevice which shows arterial stiffness. PWV, SI and RI values were obtained.All the patients underwent two dimensional and Doppler echocardiographicexamination. Glucose and lipid levels of serum and renal and liver functiontests were obtained. After these tests were resulted, thyroid hormonereplacement treatment was begun. All these tests were repeated after 6months of the patients? euthyroidic status.Data that were obtained before and after the treatment werecompared. Significant decreases were determined in SI and PWV values withthyroid hormone replacement treatment (p<0.001 and p<0.001, respectively).No significant changes were determined in RI values (p=0.261).No significant changes were determined in total cholesterol,triglyceride, LDL-cholesterol and HDL- cholesterol levels of serum withlevothyroxine treatment. Significant decreases were determined in bodymass index (p<0.001).No significant differences were determined in EDD, ESD, IVST, PWTand EF parameters of the left ventricle. Significant decrease was determined48in MPI (p<0.001). Significant increase in mitral E/A ratio (p<0.001) anddecrease in IRT (p<0.01). However, no significant changes were determinedin maximum mitral E and A wave velocities.In conclusion, if subclinic hypothyroidism is treated with thyroidhormone replacement successfully, arterial stiffness will decrease in longterm and this will result in the decrease of atherosclerosis development andcardiovasculary mortality. In these patients, decreasing in arterial stiffness isindependent from the lipid prophile. Moreover, treatment of thyroid hormonereplacement has also positive effects on the diastolic functions of leftventricle. This subject needs further evaluations with larger trials.