Endocrine Abstracts (2011) 26 P42

Evaluation of the effect of L-thyroxine therapy on endothelial functions in patients with subclinical hypothyroidism

Fatma Alibaz Oner1, Selen Yurdakul2, Ender Oner3, Ayse Kubat Uzum4 & Mecdi Erguney5

1Marmara University Faculty of Medicine, Rheumatology, Istanbul, Turkey; 2Cardiology Division, Istanbul Florence Nightingale Hospital, Istanbul, Turkey; 3Coronary Intensive Care Unit, Istanbul Education and Research Hospital, Istanbul, Turkey; 4Istanbul Education and Research Hospital, Endocrinology and Metabolism, Istanbul, Turkey; 5Education and Research Hospital, Clinic of Internal Medicine, Istanbul, Turkey.

Objectives: Subclinical hypothyroidism (SH) is characterized by normal serum free T4 (FT4), free T3 (FT3) levels and increased serum TSH levels. Endothelial dysfunction that is accepted an early step of the atherosclerosis, has been reported in patients with subclinical hypothyroidism. The aim of this study was to eveluate endothelial functions and the effect of L-thyroxine (L-T4) therapy on endothelial functions in SH.

Methods: Twenty-seven patients with SH and 22 healthy controls were evaluated by brachial ultrasonography for endothelial functions. After restorating euthyroidism in SH, measurements were repeated.

Results: The patients with subclinical hypothyroidism and healthy control group were similar in terms of baseline and nitrate induced diameters of brachial artery. Compared to the control group, the patients with SH showed significantly reduced FMD. The baseline and nitrate induced diameters of brachial artery were significantly high after L-T4 in SH group. Besides, FMD significantly increased in patients with SH.

Conclusions: Hypothyroidism accelerates atherogenesis through modification of atherosclerotic risk factors and direct effects on the blood vessels. In the present study, we found significantly improvement in FMD with L-T4 therapy. This improvement in endothelial function could translate into reduction in cardiovascular mortality and morbidity.

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