Relationships between Spleen , Platelets and Factor VIII Levels

P HYSIOLOGIC ELEVATIONS of Factor VIII occur in health and disease and are either transient or sustained (Table 1 ).l.17 The same stressful stimuli that produce transient increases in Factor VIII, notably adrenalin or exercise, also produce transient elevations of circulating platelets.182#{176} Since the platelet response is abolished by splenectomy, in the present work it was of interest to compare changes in platelet and Factor VIII levels during adrenalin infusions in individuals with and without spleens. These studies showed that Factor VIII elevations in response to adrenalin are dependent on the presence of the spleen. Although there seems to be no common basis for chronic Factor VIII elevation in the diseases listed in Table 1, a number of the disorders are associated with thrombocytopenia. Studies on a group of patients with chronic thrombocytopenia or thrombocytosis showed that an inverse relationship frequently is present between platelet and Factor VIII levels. In vitro attempts to demonstrate either an inverse or direct relationship between platelet and Factor VIII levels in the presence and absence of adrenalin were not successful, and transfusion of platelets into thrombocytopenic recipients did not significantly alter their Factor VIII levels.