Plasma von Willebrand factor antigen concentration in dogs with hypothyroidism

Plasma von Willebrand factor antigen concentration was measured in 10 dogs with hypothyroidism, before and after administration of a replacement dose of levothyroxine for 67 +/- 12 days. Results were reported as a percentage of normal activity, with plasma pooled from clinically normal dogs given a value of 100%. Plasma von Willebrand factor antigen concentration was within reference limits in dogs with hypothyroidism (126 +/- 41%) and was significantly (P < 0.01) decreased (94 +/- 39%) after treatment with levothyroxine. Contrary to findings in some other studies, a deficiency of plasma von Willebrand factor did not appear to result from hypothyroidism.