Serum fructosamine concentration in cats with overt hyperthyroidism.
OBJECTIVE
To determine the effect of hyperthyroidism on serum fructosamine concentration in cats.


METHODS
Cohort study.


METHODS
22 cats with overt hyperthyroidism.


METHODS
Hyperthyroidism was diagnosed on the basis of clinical signs, detection of a palpable thyroid gland, and high total serum thyroxine (T4) concentrations. Hyperthyroid cats with abnormal serum albumin, total protein, and glucose concentrations were excluded from the study. Samples for determination of serum fructosamine concentration were obtained prior to initiating treatment. Results were compared with fructosamine concentrations in healthy cats, cats in which diabetes had recently been diagnosed, and cats with hypoproteinemia. In 6 cats, follow-up measurements were obtained 2 and 6 weeks after initiating treatment with carbimazole.


RESULTS
Serum fructosamine concentrations ranged from 154 to 267 mumol/L (median, 198 mumol/L) and were significantly lower than values in healthy cats. Eleven (50%) of the hyperthyroid cats had serum fructosamine concentrations less than the reference range. Serum fructosamine concentrations in hyperthyroid, normoproteinemic cats did not differ from values in hypoproteinemic cats. During treatment, an increase in serum fructosamine concentration was detected.


CONCLUSIONS
In hyperthyroid cats, concentration of serum fructosamine may be low because of accelerated protein turnover, independent of blood glucose concentration. Serum fructosamine concentrations should not be evaluated in cats with overt hyperthyroidism and diabetes mellitus. Additionally, concentration of serum fructosamine in hyperthyroid cats should not be used to differentiate between diabetes mellitus and transitory stress-related hyperglycemia.
Reusch
C E
CE
Clinic for Small Animal Internal Medicine, Faculty of Veterinary Medicine, University of Zurich, Switzerland.
Tomsa
K
K
D000818:Animals; D013956:Antithyroid Agents / Q000627:therapeutic use; D001786:Blood Glucose / Q000032:analysis; D001798:Blood Proteins / Q000032:analysis; D002231:Carbimazole / Q000627:therapeutic use; D002371:Cat Diseases / Q000097:blood*; D002415:Cats; D015331:Cohort Studies; D003920:Diabetes Mellitus / Q000097:blood / Q000662:veterinary; D005260:Female; D005500:Follow-Up Studies; D019270:Fructosamine / Q000097:blood*; D006980:Hyperthyroidism / Q000097:blood / Q000188:drug therapy / Q000662:veterinary*; D007019:Hypoproteinemia / Q000097:blood / Q000662:veterinary; D008297:Male; D012016:Reference Values; D012709:Serum Albumin / Q000032:analysis
D013956:Antithyroid Agents; D001786:Blood Glucose; D001798:Blood Proteins; D012709:Serum Albumin; D019270:Fructosamine; D002231:Carbimazole