Antithrombin III deficiency in diabetes mellitus: influence on vascular degenerative complications.

Plasma Antithrombin III (At III), a natural inhibitor of coagulation, was determined using a single radial immunodiffusion technique. In 116 diabetics, plasma At III levels were significantly decreased (26.6 +/- 0.4 mg/100 ml) compared with those in 64 controls (31.0 +/- 0.3 mg/100 ml, P less than 0.001). An elevation of plasma fibrinogen degradation products in 42 per cent of our patients, and a positive linear relationship between platelet counts and At III levels ( r = 0.29, P less than 0.01), provided additional evidence for chronic disseminated intravascular clotting in diabetes mellitus. Diabetic retinal complications were more frequent in patient with low plasma At III levels (50.6 per cent of cases) than in those exhibiting At III concentrations within a normal range: 32.4 per cent of cases (X2 = 6.09, P less than 0.02). It is postulated that the low levels of At III encountered in diabetes result from excessive consumption, and that the deficiency may be responsible for the onset and/or aggravation of intravascular clotting. At III deficiency may therefore contribute to vascular degenerative complications, particularly those leading to diabetic retinopathy.