EFFECTS OF HORMONES OF THE HYPOTHALAMIC-PITUITARY-THYROID AXIS ON ACTIVITIES AND CONCENTRATIONS OF PLASMA CLOTTING FACTOR VIII AND VON WILLEBRAND FACTOR IN RATS

Effects of the hormones of the hypothalamic-pituitary-thyroid axis on the plasma levels and activities of factor VIII (F VIII) and von Willebrand factor (vWF) are studied on 65 male Wistar rats. Factor VIII: Ag, Factor VIII: C, vWF: Ag, vWF: CB, vWF: Rco activity, activated partial thromboplastine time (aPTT) and prothrombine time (PT) were determined on automatic coagulometer and ELISA reader. Thyreotropin releasing hormone (0.06 mg/kg b.w.), Thyreotropin (1 MU/kg b.w.), Liothyroninum (0.08 mg/kg b.w.), Levothyroxinum (0.08 mg/kg b.w.), applied s.c. for three consecutive days on four different groups of rats, significantly increased antigen levels of F VIII and vWF, but decreased their activities and extended aPTT and PT. These data indicate that each of the hormones applied inflicts significant changes in hemostasis by suppressing the coagulability both via intrinsic and extrinsic pathways and decreasing F VIII and vWF plasma activities.