Serum free thyroxine concentration in healthy dogs, dogs with hypothyroidism, and euthyroid dogs with concurrent illness.
ABSTRACT Serum free thyroxine (fT4), thyroxine (T4), and 3,5,3'-triiodothyronine (T3) concentrations were determined in 62 healthy dogs, 51 dogs with hypothyroidism, and 59 euthyroid dogs with concurrent dermatopathy or concurrent illness for which hypothyroidism was a diagnostic consideration. Status of thyroid function was based on history, physical findings, results of thyrotropin response testing, requirement for thyroid hormone replacement therapy, and in 31 dogs, on results of histologic examination of a thyroid gland biopsy specimen. Serum fT4 concentration was determined, using a single-stage radioimmunoassay. Mean (+/- SD) serum fT4 concentration was significantly (P less than 0.05) greater in healthy dogs vs dogs with hypothyroidism (0.51 +/- 0.27 ng/dl vs 0.10 +/- 0.07 ng/dl). Significant difference in mean serum fT4 concentration was not evident between dogs with hypothyroidism and euthyroid dogs with hyperadrenocorticism (0.16 +/- 0.13 ng/dl) or peripheral neuropathy (0.19 +/- 0.10 ng/dl). Mean serum fT4 concentration in all other groups of euthyroid dogs with concurrent illness was similar to values in healthy dogs and was significantly (P less than 0.05) greater, compared with values in dogs with hypothyroidism. Similar results were found for mean serum T4 concentration. Comparison of serum fT4 vs T4 concentration revealed: sensitivity, 0.97 vs 0.98; specificity, 0.78 vs 0.73; predictive value for a positive test result, 0.79 vs 0.80; predictive value for a negative test result, 0.97 vs 0.97; and accuracy, 0.78 vs 0.86, respectively. Ten (17%) and 12 (20%) of 59 serum fT4 and T4 concentrations, respectively, were inappropriately low in euthyroid dogs with concurrent illness.(ABSTRACT TRUNCATED AT 250 WORDS)
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ABSTRACT: The effects of spontaneous and experimentally induced congestive heart failure on serum thyroxine (T4), 3,5,3'-triiodothyronine (T3), 3,3'5'-triiodothyronine (reverse T3), free T4, free T3 concentrations, and the serum T4 and T3 concentrations in response to administration of thyrotropin were studied. Serum thyroid hormone concentrations were not different between eight dogs with spontaneous congestive heart failure and normal age matched control dogs. Seven dogs with experimental heart failure were tested before and after induction of congestive heart failure by rapid ventricular pacing. Mean serum T4 and free T3 concentrations were decreased and mean serum reverse T3 concentration was increased following induction of heart failure. The serum T4 and T3 responses to thyrotropin were not altered. Thyroid gland morphology appeared normal in dogs with experimental heart failure. Experimental congestive heart failure, similar to some other nonthyroidal illnesses, alters thyroid hormone secretion and metabolism in dogs.Canadian journal of veterinary research = Revue canadienne de recherche vétérinaire 08/1994; 58(3):157-62. · 0.94 Impact Factor
Article: Assessment of criteria used by veterinary practitioners to diagnose hypothyroidism in sighthounds and investigation of serum thyroid hormone concentrations in healthy Salukis.[show abstract] [hide abstract]
ABSTRACT: To assess use of serum thyroid hormone concentrations by veterinarians to diagnose hypothyroidism in sighthounds and to evaluate serum thyroid hormone concentrations in healthy Salukis. Retrospective case series and cross-sectional study. 398 sighthounds of various breeds with a diagnosis of hypothyroidism and 283 healthy Salukis. Pretreatment thyroid hormone assay results from sighthounds subsequently classified as hypothyroid by practitioners were retrieved from a laboratory database. In healthy Salukis, serum concentrations of total thyroxine (T(4)), free T(4), total triiodothyronine (T(3)), free T(3), and thyroid-stimulating hormone (TSH) and antibodies against thyroglobulin and thyroid hormones were assayed. Records indicated hypothyroidism had been diagnosed in 303 (76.1%) sight-hounds on the basis of low serum thyroid hormone concentrations alone and in 30 (7.5%) others despite all thyroid hormone indices being within reference limits. Only 65 (16.3%) dogs had a high TSH concentration or positive thyroglobulin autoantibody result to support the diagnosis. In healthy Salukis, median (reference limits) serum concentrations of total T(4), free T(4), total T(3), free T(3), and TSH were 13.0 nmol/L (2.8 to 40.0 nmol/L), 12.0 pmol/L (2.0 to 30.3 pmol/L), 1.0 nmol/L (0.4 to 2.1 nmol/L), 4.0 pmol/L (1.6 to 7.7 pmol/L), and 0.18 ng/mL (0 to 0.86 ng/mL), respectively. Diagnosis of hypothyroidism by practitioners was most often made without adequate supportive laboratory evidence. Thyroid hormone values in healthy Salukis differed markedly from standard reference limits for some, but not all, thyroid hormone indices. Breed-specific reference limits should be used when interpreting thyroid hormone profiles of sighthounds.Journal of the American Veterinary Medical Association 02/2010; 236(3):302-8. · 1.79 Impact Factor