Thrombocytopenia in Graves’ Disease: Effect of T₃on Platelet Kinetics

Abstract

A study was carried out in which the platelet count was decreased in approximately half the patients with hyperthyroidism and gradually increased with treatment. Platelet disappearance curves were curvilinear and the platelet survival was shortened in the hyperthyroid state. Patients maintained in a euthyroid state for 3 months or less continued to have a shortened platelet survival. The survival returned to normal after 6 months or more of euthyroid status. In order to clarify the cause of the decreased platelet count in the patients, animal experiments were performed. T₃-injected rats had decreased platelet counts and shortened platelet survival. When platelets obtained from T₃-injected rats were transfused to a control group of untreated rats, the platelet survivals were normal. When platelets obtained from the control group of rats were transfused to T₃-injected rats, the platelet survivals were shortened. Disappearance of heat-damaged RBC from the circulation was also accelerated in T₃-injected rats. This suggests that thrombocytopenia in Graves’ disease is caused by an increased sequestration potency of the reticulo-endothelial phagocyte system stimulated by thyroid hormone.

Clinical Feasibility of Monitoring Resting Heart Rate Using a Wearable Activity Tracker in Patients With Thyrotoxicosis: Prospective Longitudinal Observational Study (Preprint)

“…Thyrotoxicosis increases liver enzyme levels due to relative hypoxia in the hepatic perivenular regions [23,24]. Although reports have conflicted, relatively low platelet counts in thyrotoxic patients has also been reported [25,26]. Our baseline results were consistent with these previous reports.…”

Coagulation and fibrinolysis in thyroid dysfunction

“…For compensation, the number of megakaryocytes and circulating young thrombocytes increase. As the young thrombocytes are bigger than mature ones, an increase in MPV is also observed [7,15].…”

Thyroid-associated autoimmune coagulation disorders

“…Similar to the results from Palareti et al, these platelet changes normalized during L-thyroxine treatment, suggesting that the prolonged primary hemostasis in hypothyroidism is a consequence of thyroid hormone status. Kurata et al [14] studied 214 patients with Graves' disease and found that approximately half of them had a low platelet count and shortened platelet survival which returned to normality after antithyroid treatment. Similarly, Panzer et al [15] studied 15 patients with hyperthyroidism and found a low median platelet count, an increased mean platelet volume, and a shortened platelet lifespan.…”