Thyroid Dysfunction and Hemostasis: An Issue Still Unresolved

Abstract

Thyroid hormones exert various effects on the hemostatic system, as documented by the fact that subclinical or overt thyroid dysfunctions may be associated with hypocoagulable or hypercoagulable states. In this review, the hemostatic balance (primary hemostasis, coagulation factors, and fibrinolytic system) in different thyroid disorders is analyzed from a laboratory, pathogenic, and clinical point of view. Although limited, the published studies suggest that patients with hyperthyroidism or subclinical hypothyroidism have an increased thrombotic risk, whereas patients with overt hypothyroidism have a bleeding tendency. Further trials on larger series of patients are needed to confirm these preliminary findings and to elucidate the pathogenic mechanisms regulating the complex interaction between thyroid disorders and hemostasis.

Prevalence and characteristics of anemia associated with thyroid disorders in non-pregnant Saudi women during the childbearing age: A cross-sectional study

“…T hyroid hormones are essential for the normal development, differentiation, metabolic balance, and physiological function of virtually all tissues [1] and thyroid function disorders are among the most common endocrine diseases. [2][3][4][5] Thyroid disorders affect females more than males, especially during the reproductive age.…”

“…[6,7,10] Alternatively, hyperthyroidism is less prevalent with a frequency ranging between 0.5 and 2% in women. [1,3,[10][11][12][13][14][15] Thyroid disorders are associated with hematological abnormalities and anemia is the most prevalent disorder. [6,12,[16][17][18] Early reports have shown a decrease in the number of red blood cells (RBCs) in the peripheral blood of patients after thyroidectomy [19] and anemia has been defined in 20-60% of the patients with hypothyroidism.…”

Negative association between free triiodothyronine level and international normalized ratio in euthyroid subjects with acute myocardial infarction

“…In present study, among of 231 patients, 23% were lower than the normal reference of FT3 (3.1 pmol/L). Thyroid hormones exert various effects on the coagulation system [19] . Modulation of the levels of T3 in hyper-and hypothyroidism is extremely important for the capability to increase or decrease the concentrations of fibrinogen and numerous blood clotting factors [20] .…”

“…Several biological mechanisms have been proposed to explain this intriguing association, including the effects of thyroid hormones on the synthesis of coagulation factors and the thyroid-related autoimmune processes [13,19] . However, the exact mechanism underlying the relationship between FT3 and INR remains unclear.…”

The even closer link between the thyroid and haemostasis

“…The close relationship between thyroid hormones and the coagulation system has been known since the beginning of the past century and has been analysed over the decades by several investigators (1). Accordingly, various haemostatic abnormalities, involving both primary haemostasis and the coagulation/fibrinolytic system, have been reported in patients affected by a wide variety of endocrine disorders and range from subclinical laboratory abnormalities to clinically relevant haemorrhagic or thrombotic events (2)(3)(4)(5).…”