Effect of levothyroxine administration on hemostatic analytes in Doberman Pinschers with von Willebrand disease

• Published in: Journal of veterinary internal medicine Vol. 19; no. 4; pp. 523 - 527
• Main Authors: Heseltine, J.C, Panciera, D.L, Troy, G.C, Monroe, W.E, Brooks, M.B, Feldman, B.F
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-07-2005
• Subjects: Animals; blood coagulation disorders; Canine; Cross-Over Studies; Dog Diseases - blood; Dog Diseases - drug therapy; Dogs; Double-Blind Method; Female; Hemostasis - drug effects; L-thyroxine; Male; Thyroid; Thyrotropin - blood; Thyroxine - blood; Thyroxine - therapeutic use; Triiodothyronine - blood; von Willebrand Diseases - blood; von Willebrand Diseases - drug therapy; von Willebrand Diseases - veterinary; von Willebrand factor
• ISSN: 0891-6640; 1939-1676
• DOI: 10.1111/j.1939-1676.2005.tb02721.x

Levothyroxine administration has been suggested to be an effective treatment for canine von Willebrand disease (vWd), but evidence supporting this treatment is lacking. Effects of levothyroxine administration were evaluated in 8 euthyroid Doberman Pinschers with plasma von Willebrand factor (vWf) concentrations <15%, characteristic of type 1 vWd. Levothyroxine (0.04 mg/kg PO q12h) and placebo were administered for 30 days in a 2‐period, 2‐treatment, double‐blinded, crossover design with a 30‐day washout period between treatments. Buccal mucosal bleeding time (BMBT), plasma vWf concentration (vWf: Ag), vWf collagen binding activity (vWf:CBA), factor VIII coagulant activity (FVIII:C), and serum concentrations of total thyroxine (T4), free thyroxine (fT4), 3,5,3′‐triiodothyronine (T3), and thyroid‐stimulating hormone (TSH) were measured on days 0, 2, and 30 of each treatment period. The 8 dogs (1 male, 7 females) had markedly low plasma vWf:Ag (mean, 8.9%; reference range, 70–180%) and vWf:CBA (mean, 11.1%; reference range, >70%). Response to placebo versus levothyroxine treatment was not significantly different between groups at day 0, 2, or 30 for BMBT, vWf: Ag, vWf: CBA, and FVIII: C. Serum T4, fT4, and T3 concentrations were significantly higher and serum TSH significantly lower in the levothyroxine‐treated group than in the placebo group at days 2 and 30. Administration of levothyroxine at 0.04 mg/kg caused laboratory evidence of hyperthyroidism but did not affect plasma FVIII:C and vWf: Ag concentrations or vWf‐dependent collagen binding and BMBT. The results of this study failed to identify a direct action of levothyroxine supplementation on plasma vWf concentration or activity in euthyroid Doberman Pinschers with vWd.