Coronary flow reserve after l-thyroxine therapy in Hashimoto’s thyroiditis patients with subclinical and overt hypothyroidism

Abstract

Overt and subclinical hypothyroidism are reported to be associated with increased cardiovascular disease risk. We have used coronary flow reserve (CFR) measurement by trans-thoracic Doppler echocardiography (TTDE) to determine coronary microvascular function in Hashimoto's thyroiditis patients with overt and subclinical hypothyroidism and to evaluate effects of L-thyroxine replacement on coronary endothelial function. In total, 10 overt hypothyroid patients, 10 subclinical hypothyroid patients, and 10 controls were enrolled. FT4, TSH, anti-thyroid antibodies, lipid profile, insulin, glucose, HOMA-IR, physical parameters, and CFR measured by TTDE were recorded before and after 6 months of L: -thyroxine replacement in all groups. CFR values of all hypothyroid patients at baseline were significantly lower than those in controls. After L: -thyroxine, CFR increased significantly in overt and subclinical hypothyroidism with respect to the baseline measurements (P < 0.05). When baseline and second measurements were evaluated collectively for patients and controls, CFR was positively correlated with FT4 levels (r = 0.31, P = 0.01) and negatively correlated with TSH and HOMA-IR (r = -0.38, P = 0.002 and r = -0.42, P < 0.001, respectively). Subclinical as well as overt hypothyroid patients have impaired coronary microvascular function which improved after L: -thyroxine therapy. Treatment of Hashimoto's thyroiditis patients with subclinical hypothyroidism should be considered to improve cardiovascular disease risk.