Increased levels of free thyroxine and risk of venous thrombosis in a large population-based prospective study.
J Thromb Haemost. 2012 Jun 15;
Authors: Debeij J, Dekkers O, Asvold B, Christiansen S, Naess I, Hammerstrom J, Rosendaal F, Cannegieter S
Background: Recent studies have shown that high levels of free thyroxine (FT4), even without leading to hyperthyroidism, are associated with a procoagulant state. Objectives: The aim of our study was to determine whether high levels of thyroid hormones are associated with an increased risk of venous thrombosis. Patients/Methods: From a prospective nested case-cohort design within the Norwegian HUNT2 cohort (1995 - 1997; 66 140 subjects) all patients with venous thrombosis during follow-up (n=515) and 1476 randomly selected age and sex-stratified controls were included. Relative and absolute risks for venous thrombosis were calculated for different cut-off levels of thyroid hormones based on percentiles in the controls. and different times between blood sampling and event, Results: In subjects with a FT4 level above the 98th percentile (17.3 pmol/l) the odds ratio (OR) was 2.5 (CI95 1.3 to 5.0) compared with subjects with levels below this percentile. For venous thrombosis within one year from blood sampling, this relative risk was more pronounced with an OR of 4.8 (CI95 1.7 to 14.0). Within half a year the association was even stronger with an OR of 9.9 (CI95 2.9 to 34.0, adjusted for age, sex and BMI). For TSH the relation was inverse and less pronounced. The absolute risk within 6 months in the population for FT4 levels above the 98th percentile was 6.1 per 1000 person-years (CI95 1.7 to 15.7). Conclusions: Levels of free thyroxine at the upper end of the normal range are a strong risk factor for venous thrombosis. The risk increased with higher levels of thyroxine and shorter time between blood sampling and event. Further studies into the effect of clinical hyperthyroidism are warranted. © 2012 International Society on Thrombosis and Haemostasis.
PMID: 22703181 [PubMed - as supplied by publisher]