Endothelial function in patients with hyperthyroidism before and after treatment with propranolol and thiamazol

Hyperthyroidism is associated with a higher incidence of arterial thromboem bolism; increasing age, atrial fibrillation, and mitral valve abnormalities are risk factors. However, the contribution of endogenous coagulation para meters is unclear. Because thyroid hormone influences receptor and transcri ption factors, it can be expected that it will influence proteins involved in coagulation processes synthetised in many cells. Fourteen hyperthyroid patients were studied untreated, after 1 week of trea tment with propranolol, and after therapeutic treatment with thiamazol. Fou rteen matched controls were used for comparison. On each occasion, endothel ial marker proteins, coagulation/fibrinolysis factors, and inflammatory (li ver) markers were measured. Excess thyroid hormone was associated with elevated levels of most endothel ium-associated proteins. In addition, plasma fibronectin and fibrinogen wer e increased, while plasminogen was decreased. No evidence was found that hy perthyroidism was associated with coagulation/fibrinolysis activation, or w ith increased levels of the inflammation markers interleukin-6 (IL-6), tumo r necrosis factor-alpha (TNF-alpha) or C-reactive protein (CRP). Propranolo l treatment only lowered the von Willebrand factor propeptide, and slightly increased plasminogen. Treatment with thiamazol returned all parameters to normal. Hyperthyroidism increased the plasma levels of most endothelial ma rker proteins, and of some liver-synthetized proteins. No evidence for coag ulation/fibrinolysis activation was found. However, it appears that endothe lial activation, which is indicative of a procoagulant state, is present in hyperthyroidism. This may explain the association between hyperthyroidism and thromboembolism especially if other risk factors are present. von Wille brand factor II (vWF:Ag-II) levels may be suitable markers to evaluate acut e changes in endothelial function because this parameter responds more rapi dly to changes in endothelial function than other factors.