Endocrine Abstracts

Background: Thyroid hormone plays a potent role in many physiological processes, including the impact on blood coagulation. But, there are some contradictory results on the effect of hypothyroidism on the changes in homeostasis. Venous thromboembolism (VTE), commonly defined as deep vein thrombosis (DVT) or pulmonary embolism (PE), is a major health problem worldwide. Little was known about the association between hypothyroidism and VTE. Our study aimed to evaluate the association between hypothyroidism and VTE, and the possible effect of levothyroxine treatment on risks of VTE in hypothyroidism group.

Design: Nationwide population-based retrospective cohort study.

Setting: Taiwan’s National Health Insurance Research Database.

Participants: Individuals with (n=5,488) and without (n=21,952) hypothyroidism.

Measurement: Individuals with and without hypothyroidism were matched 1:4 for age, sex, and index year. Those with hypothyroidism were further divided into levothyroxine treatment and without levothyroxine treatment. Incidences and hazard ratios (HR) for risks of developing VTE were calculated using Cox proportional hazard regression models. Deep vein thrombosis and pulmonary embolism were analyzed individually.

Results: During mean follow-up of 6.9 years, 89 participants in the hypothyroidism cohort and 214 participants in the non-hypothyroidism cohort developed VTE events. Having hypothyroidism was significantly associated with risk of developing VTE events and DVT (adjusted HR (aHR)=1.34, 95% confidence interval (CI)=1.04–1.74, P=0.026, DVT: aHR=1.33, 95% CI=1.01–1.75, P=0.044). But, there was no associated with risk of developing PE. We also analyses the effect of levothyroxine. Hypothyroidism without levothyroxine had the greater risk of of developing VTE events and DVT (VTE: aHR=1.82, 95% CI=1.24–2.67, P=0.002, DVT: aHR=1.76, 95% CI=1.17–2.65, P=0.0007). Besides, hypothyroidism with age younger than 40 were associated with greater risk of developing VTE (multivariate mode, adjusted HR=2.4, 95% CI=1.14–5.05, P=0.02). However, there was no statically associated with risk of developing VTE events and DVT in hypothyroidism treated with levothyroxine (VTE: adjusted HR=1.17, 95% CI=0.86–1.58, P=0.311, DVT: aHR=1.14, 95% CI=0.83–1.58, P=0.417), even in any age and gender.

Conclusion: Hypothyroidism was independently associated with increased risks of VTE and DVT. However, hypothyroidism treated with levothyroxine did not have association with increased risks of VTE and DVT.