Njurfunktion hos hypertyreoida katter
en jämförelse mellan serumkreatinin och serumcystatin C
Hyperthyroidism and chronic kidney failure (CKD) are common diseases in older cats. It can be difficult to evaluate kidney function in cats suffering from both conditions simultaneously. In the daily clinic serum creatinine is the analysis of choice when evaluating kidney function and secondary glomerular filtration rate (GFR). This marker does not, however, detect kidney damage until about 75 % of the function is lost. There are several other techniques available when investigating GFR but none are readily available for the small clinic. It would be of great interest if there was a marker that could be analyzed from a simple blood sample and that illustrates GFR better than serum creatinine.
Since several years there is such a marker available in human medicine, serum cystatin C (CysC) that has been claimed to be superior to serum creatinine. The present study was performed to evaluate kidney function in hyperthyroid cats and whether CysC is useful in cats also. Samples from 32 consecutive cats (8 euthyroid and 24 hyperthyroid) were selected and analyzed for serum creatinine and CysC. The hyperthyroid cats had all been treated with either methimazole or radioactive iodine. The results of this study indicate a correlation between serum creatinine and CysC in cats. The euthyroid cats had generally lower serum levels of both creatinine and cystatin C than cats in the hyperthyroid group. Noticeably cats in both groups seemed to have higher levels of CysC than humans.
Further studies are required before CysC can be an alternative to serum creatinine in daily practice considering kidney function in cats. There is also a need for establishing reference values in cats.