Hyperthyroidism is associated with several changes in the haemostatic system resulting in a hypercoagulable state. It is uncertain at this stage whether this leads to an increased risk of venous thromboembolism (VTE). The aim of this retrospective cohort study was to determine the risk of VTE in all patients with overt hyperthyroidism and to compare this to the risk of VTE in the general population. In three hospitals in the Netherlands, patients with biochemically confirmed hyperthyroidism caused by Graves' disease, multinodular goiter or toxic adenoma were included. All available electronic and handwritten records were examined. Primary outcome was the occurrence of VTE within six months before and until six months after the diagnosis of hyperthyroidism. We included a total of 587 patients. Five patients experienced a VTE during the study period, resulting in an incidence rate of 8.7 (95% CI 2.8 - 20.2) per 1,000 person-years. Three of these five patients had a first VTE (incidence rate for first VTE was 5.3 [95% CI 1.1 - 15.6] per 1,000 person-years). Incidence rates of VTE in the general population are between 0.6 and 1.6 per 1,000 person-years for first VTE and 0.7 and 1.8 per 1,000 person-years for all VTE. In conclusion, the incidence rate of VTE in patients with hyperthyroidism appears to be high. Future prospective studies are needed to further explore this possible association and to address its clinical implications.
"Clinical evidence indicates that hyperthyroidism increases the risk of arterial thromboembolism  and unprovoked venous thrombosis   . Hypothyroidism is also associated with increased venous thromboembolism (VTE) risk . "
[Show abstract][Hide abstract] ABSTRACT: Introduction
Available data on fibrin clot properties and fibrinolysis in hyperthyroidism and hypothyroidism are inconsistent. Our objective was to assess the impact of effective treatment of hyper- and hypothyroidism on fibrin clot characteristics.
Material and Methods
In a case-control study, ex vivo plasma fibrin clot permeability (Ks) and efficiency of fibrinolysis were assessed in 35 consecutive hyperthyroid and 35 hypothyroid subjects versus 30 controls. All measurements were performed before and after 3 months of thyroid function normalizing therapy.
At baseline, hyperthyroid, but not hypothyroid, patients had lower Ks than controls (p < 0.0001). Hyperthyroid and hypothyroid groups compared with controls had prolonged clot lysis time (CLT), and lower rate of D-dimer release from clots (D-Drate) (all p < 0.05). The regression analysis adjusted for fibrinogen showed that in hyperthyroid patients, pre-treatment thyroid stimulating hormone (TSH) independently predicted Ks, while thrombin activatable fibrinolysis inhibitor (TAFI) antigen predicted CLT. In hypothyroid individuals a similar regression model showed that TSH independently predicts CLT. After 3 months of thyroid function normalizing therapy, 32 (91.4%) hyperthyroid and 30 (85.7%) hypothyroid subjects achieved euthyroidism and had improved fibrin clot properties (all p < 0.05), with normalization of Ks in hyperthyroid and lysability in hypothyroid patients.
Both hyper- and mild-to-moderate hypothyroidism are associated with prothrombotic plasma fibrin clot phenotype and restoration of euthyroidism improves clot phenotype. Abnormal fibrin clot phenotype might contribute to thromboembolic risk in thyroid disease.
Thrombosis Research 08/2014; 134(2). DOI:10.1016/j.thromres.2014.05.041 · 2.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Several coagulation and fibrinolytic parameters appear to be affected by thyroid hormone excess; however, the net effect on the haemostatic system remains unclear. We aimed to update our previous review and systematically summarise and meta-analyse the data by assessing the effects of thyrotoxicosis on the coagulation and fibrinolytic system in vivo . Data sources included MEDLINE (2006-2012), EMBASE (2006-2012), and reference lists. The sources were combined with our previous search containing studies from 1980-2006. Eligible studies were all observational or experimental studies. Two investigators independently extracted data and rated study quality. Weighted mean proportion and 95% confidence intervals were calculated and pooled using a fixed and a random-effects model. A total of 29 articles consisting of 51 studies were included, as in several articles more than one study was described. We included four intervention (before and after treatment in hyperthyroid patients), five cross-sectional (hyperthyroid subjects and euthyroid controls), and four experimental (before and after use of thyroid hormone in euthyroid subjects) medium/high quality studies for meta-analysis. We found that thyrotoxicosis shifts the haemostatic balance towards a hypercoagulable and hypofibrinolytic state with a rise in factors VIII and IX, fibrinogen, von Willebrand factor, and plasminogen activator inhibitor-1. This was observed in endogenous and exogenous thyrotoxicosis, and in subclinical as well as overt hyperthyroidism. We conclude that both subclinical and overt hyperthyroidism induce a prothrombotic state, which is therefore likely to be a risk factor for venous thrombosis.
Thrombosis and Haemostasis 09/2012; 108(6). DOI:10.1160/TH12-07-0496 · 4.98 Impact Factor
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