Effect of Levothyroxine Administration on Hemostatic Analytes in Doberman Pinschers with von Willebrand's Disease

This study tested the hypothesis that levothyroxine supplementation increases plasma von Willebrand factor (vWf) concentration and enhances vWf function. The effects of levothyroxine administration were evaluated in 8 euthyroid Doberman Pinschers with plasma vWf concentration <30%. Levothyroxine (0.04mg/kg PO q12hours) 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), vWf antigen concentration (vWf:Ag), vWf collagen binding activity (vWf:CBA), Factor VIII coagulant activity (FVIII:C), serum total thyroxine (T4), free thyroxine (fT4), 3,5,3â -triiodothyronine (T3), and thyroid stimulating hormone were measured on days 0, 2, and 30 of each treatment period. The dogs had markedly low plasma vWf:Ag concentrations (mean 8.9%; reference range 70-180%) and vWf:CBA (mean 11.1%; reference range >70%). All dogs had FVIII:C activity within reference range. The response to placebo versus active levothyroxine treatment revealed no significant differences between groups at any time for BMBT, vWf:Ag, vWf:CBA, and FVIII:C. Serum total thyroxine, fT4, and T3 were significantly higher in the levothyroxine-treated group compared to the placebo group at days 2 and 30. Thyroid stimulating hormone was significantly lower in the levothyroxine-treated group compared to the placebo group at days 2 and 30. Levothyroxine (0.04mg/kg) caused laboratory evidence of hyperthyroidism but did not affect plasma FVIII:C and vWf:Ag concentration or the vWf-dependent functional parameters of collagen binding and BMBT. The results of this study do not reveal a direct action of levothyroxine supplementation on plasma vWf concentration or activity in euthyroid Doberman Pinschers.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Veterinary Medical Sciences

Department dc:contributor.department

Veterinary Medical Sciences

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2004

Author dc:creator

• Heseltine-Heal, Johanna Colleen

Chair dc:contributor.committeechair

• Panciera, David L.

Committee members dc:contributor.committeemember

• Monroe, William E.
• Feldman, Bernard F.
• Troy, Gregory C.

• levothyroxine
• thyroid
• canine
• von Willebrand's disease
• von Willebrand factor

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-05042004-224809

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/32178