EFFECTS OF THE HORMONES OF THYROID HORMONAL AXIS (TRH, TSH, T3 AND T4) ON PLASMA COAGULATION FACTORS V, XI, XII AND XIII IN THE RAT

The subtle balance between the multiple factors, cofactors, inhibitors and activators involved in hemostasis is precisely maintained via various regulatory mechanisms, including the endocrine system. However, the role of the hormones of thyroid hormonal axis in this regulation is not clearly defined. The study is designed to investigate the effects of the hormones of the hypothalamic-pituitary-thyroid hormonal axis (TRH, TSH, T3 and T4) on plasma activity of clotting factors V, XI, XII and XIII in rats. The experiments were carried out on 65 male Wistar rats. The hormones were injected subcutaneously once daily for three consecutive days in the following doses: TRH - 0.06 mg/kg body mass, TSH - 1 IU/kg, T3 and T4 - 0.08 mg/kg. Plasma activities of coagulation factors V, XI, XII and XIII were determined by Dade Behring tests. The results of this study indicate that the hormones of hypothalamic-pituitary thyroid hormonal axis are substantially involved in the regulation of haemocoagulation in rats by modulating in different patterns the activities of clotting factors V, XI, XII and XIII. TRH and TSH suppressed (p < 0.001) factors V and XII, increased factor XIII (p < 0.001) activity and did not affect factor XI. T3 and T4 did not inflict any significant effects on factor V, but decreased the activity of factors XI, XII and XIII (p < 0.001). These results evidence the hormones of thyroid hormonal axis modulate the initial triggering mechanism of activation of haemocoagulation through the intrinsic pathway via factors XII and XI; the intermediate common pathway steps via effects on factor V; and the last step of fibrin stabilization via factor XIII.