Objective—To evaluate the effect of trilostane on
serum concentrations of aldosterone, cortisol, and
potassium in dogs with pituitary-dependent hyperadrenocorticism
(PDH), compare the degree of reduction
of aldosterone with that of cortisol, and compare
aldosterone concentrations of healthy dogs with
those of dogs with PDH.
Animals—17 dogs with PDH and 12 healthy dogs.
Procedure—For dogs with PDH, the initial dose of
trilostane was selected in accordance with body
weight. A CBC count, serum biochemical analyses,
and ACTH stimulation tests were performed in each
dog. Dogs were evaluated 1, 3 to 4, 6 to 8, and 10 to
12 weeks after initiation of treatment. Healthy dogs
were evaluated only once.
Results—Serum aldosterone concentrations before
ACTH stimulation did not change significantly after initiation
of treatment with trilostane. At each evaluation
after initiation of treatment, serum aldosterone concentrations
after ACTH stimulation were significantly
lower than corresponding concentrations before initiation
of treatment. The overall effect of trilostane on
serum aldosterone concentration was less pronounced
than the effect on serum cortisol concentration.
Median potassium concentrations increased
slightly after initiation of treatment with trilostane.
Dogs with PDH had significantly higher serum aldo
sterone concentrations before and after ACTH stimulation
than healthy dogs.
Conclusions and Clinical Relevance—Treatment
with trilostane resulted in a reduction in serum cortisol
and aldosterone concentrations in dogs with PDH,
although the decrease for serum aldosterone concentration
was smaller than that for serum cortisol concentration.
There was no correlation between serum
concentrations of aldosterone and potassium during
treatment. (Am J Vet Res 2004;65:1245–1250)
Objective—To evaluate 4 methods used to measure plasma insulin-like growth factor (IGF) 1 concentrations in healthy cats and cats with diabetes mellitus or other diseases.
Animals—39 healthy cats, 7 cats with diabetes mellitus, and 33 cats with other diseases.
Procedures—4 assays preceded by different sample preparation methods were evaluated, including acid chromatography followed by radioimmunoassay (AC-RIA), acid-ethanol extraction followed by immunoradiometry assay (AEE-IRMA), acidification followed by immunochemiluminescence assay (A-ICMA), and IGF-2 excess followed by RIA (IE-RIA). Validation of the methods included determination of precision, accuracy, and recovery. The concentration of IGF-1 was measured with all methods, and results were compared among cat groups.
Results—The intra-assay coefficient of variation was < 10% for AC-RIA, A-ICMA, and AEE-IRMA and 14% to 22% for IE-RIA. The linearity of dilution was close to 1 for each method. Recovery rates ranged from 69% to 119%. Five healthy cats had IGF-1 concentrations > 1,000 ng/mLwith the AEE-IRMA, but < 1,000 ng/mL with the other methods. Compared with healthy cats, hyperthyroid cats had significantly higher concentrations of IGF-1 with the A-ICMA method, but lower concentrations with the IE-RIA method. Cats with lymphoma had lower IGF-1 concentrations than did healthy cats regardless of the method used.
Conclusions and Clinical Relevance—Differences in the methodologies of assays for IGF-1 may explain, at least in part, the conflicting results previously reported in diabetic cats. Disorders such as hyperthyroidism and lymphoma affected IGF-1 concentrations, making interpretation of results more difficult if these conditions are present in cats with diabetes mellitus.