Prothrombotic changes due to an increase in thyroid hormone levels.

Abstract

OBJECTIVE:

With increasing free thyroxine levels, a gradually rising risk of venous thromboembolism has been described in case-control studies. However, reports on the influence of thyroid hormones on haemostasis, while suggesting a hypercoagulable state in thyrotoxicosis, have often been inconclusive. This study evaluates multiple markers of haemostasis and fibrinolysis in a paired design, making it more sensitive to changes in thyroid hormone levels.

DESIGN:

We analysed multiple variables in patients who shifted from severe hypothyroidism to mild hyperthyroidism during thyroid cancer treatment. Those with possible residual disease were excluded.

METHODS:

Ninety patients following total thyroidectomy were tested on two occasions: i) before radioiodine remnant ablation and ii) 6 weeks later, on levothyroxine (lT4) suppression treatment, and the results were compared using the Wilcoxon's test for paired data.

RESULTS:

During lT4 treatment, significant increases (all P<0.001) in fibrinogen (from median 3.4 to 3.8 g/l), von Willebrand factor (from 85 to 127%), factor VIII (from 111 to 148%) and plasminogen activator inhibitor 1 (from 6.5 to 13.9 μg/l) were observed. In addition, the activation times of platelet adhesion and aggregation stimulated with collagen and epinephrine (EPI)/ADP, i.e. closure times in platelet function analyser (PFA-100), were significantly shortened (P<0.001): for EPI from median 148 to 117 s and for ADP from 95 to 80 s. Changes in other tests were less prominent or insignificant.

CONCLUSIONS:

An increase in thyroid hormone levels shifts the haemostatic balance towards a hypercoagulable, hypofibrinolytic state. This may contribute to the increased cardiovascular morbidity and mortality observed even in mild thyrotoxicosis.

• Authors: Jiri Horacek, Jaroslav Maly, Ioannis Svilias, Lukas Smolej, Jitka Cepkova, Jaroslav Vizda, Petr Sadilek, Ilona Fatorova, Pavel Zak
• Journal: European journal of endocrinology (Eur J Endocrinol) Vol. 172 Issue 5 Pg. 537-42 (May 2015) ISSN: 1479-683X [Electronic] England
• PMID: 25637077 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2015 European Society of Endocrinology.

Chemical References

• Blood Coagulation Factors
• Iodine Radioisotopes
• Thyroid Hormones
• Thyroxine

Topics

• Adult
• Blood Coagulation Factors (metabolism)
• Female
• Fibrinolysis (drug effects)
• Hormone Replacement Therapy
• Humans
• Hyperthyroidism (blood, complications, etiology)
• Iodine Radioisotopes (therapeutic use)
• Male
• Platelet Function Tests
• Postoperative Complications (blood)
• Thrombosis (etiology)
• Thyroid Hormones (blood)
• Thyroid Neoplasms (metabolism, radiotherapy, surgery)
• Thyroidectomy
• Thyroxine (therapeutic use)