title: Effect of levothyroxine administration on hemostatic analytes in Doberman Pinschers with von Willebrand disease.
abstract: 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.
authors.affiliation: Department of Veterinary Clinical Sciences, Oklahoma State University, Stillwater, OK 74078, USA. heselti@okstate.edu
authors.forename: Johanna C
authors.initials: JC
authors.lastname: Heseltine
authors.forename: David L
authors.initials: DL
authors.lastname: Panciera
authors.forename: Gregory C
authors.initials: GC
authors.lastname: Troy
authors.forename: William E
authors.initials: WE
authors.lastname: Monroe
authors.forename: Marjory B
authors.initials: MB
authors.lastname: Brooks
authors.forename: Bernard F
authors.initials: BF
authors.lastname: Feldman
mesh_terms: D000818:Animals; D018592:Cross-Over Studies; D004283:Dog Diseases / Q000097:blood / Q000188:drug therapy*; D004285:Dogs; D004311:Double-Blind Method; D005260:Female; D006487:Hemostasis / Q000187:drug effects*; D008297:Male; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood / Q000627:therapeutic use*; D014284:Triiodothyronine / Q000097:blood; D014842:von Willebrand Diseases / Q000097:blood / Q000188:drug therapy / Q000662:veterinary*
chemical_list: D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine