By Gunhild Lerstad, MD/PhD in TREC
Several studies have shown that thyroid dysfunction leads to increased risk of myocardial infarction and stroke. Only two studies have investigated the association between thyroid dysfunction and venous thrombosis. Both studies report that thyroid dysfunction is associated with an increased risk of venous thrombosis.
Since there are very few studies on thyroid dysfunction and venous thrombosis, we aimed to investigate whether thyroid function, assessed by thyroid stimulating hormone (TSH), was a risk factor for venous thrombosis in the general population. TSH is known to be the most sensitive measure of thyroid dysfunction.
|Thyroid Dysfunction: The thyroid is part of the endocrine system, which is made up of glands that produce, store, and release hormones into the bloodstream so the hormones can reach the body’s cells. The thyroid gland makes two main hormones, Triiodothyronine (T3) and Thyroxine (T4). It is important that T3 and T4 levels are neither too high nor too low. To regulate these levels, the thyroid gland produce more or less of T3 and T4 by either increasing or decreasing the release of a hormone called thyroid stimulating hormone (TSH). When T3 and T4 levels are low in the blood, the pituitary gland releases more TSH to tell the thyroid gland to produce more thyroid hormones. If T3 and T4 levels are high, the pituitary gland releases less TSH to the thyroid gland to slow production of these hormones. Source: www.endocrineweb.com
We investigated 12 969 subjects from the Tromsø Study and found that subjects with normal TSH levels had no increased risk of venous thrombosis. However, both high and low TSH levels were associated with a moderate increased risk of venous thrombosis compared to those with normal TSH levels. The association between thyroid dysfunction and thrombosis was augmented for provoked venous thrombosis (cases of venous thrombosis where one or more known triggering factors are present, e.g. surgery, acute medical conditions, immobilization etc.).
The increased risk of provoked venous thrombosis observed in our study may suggest that thyroid dysfunction predispose for venous thrombosis through associated hospitalization or other diseases. Nevertheless, the low prevalence of thyroid dysfunction and the correspondingly low proportion of venous thrombotic events that could be attributed to thyroid dysfunction, suggest that thyroid dysfunction has a minor clinical impact on venous thrombosis in the general population.
Reference: Lerstad G, Enga K, Jorde R, Brodin E, Svartberg J, Braekkan S and Hansen JB. Thyroid function, assessed by thyroid stimulating hormone, and future risk of venous thromboembolism -The Tromso study. European Journal of Endocrinology. 2015.