The effects of thyroid dysfunction on levels of serum cystatin C and creatinine

Cystatin C is a cysteine proteinase inhibitor, which is synthesized at a fixed rate in all nucleated cells, freely filtered through kidney glomerules and almost completely reabsorbed and catabolized in the proximal tubules. Therefore, Serum concentrates of cystatin C are more reliable, specific and sensitive indicator for GFR, in comparison with serum creatinine concentrates. This study is planned for the purpose of pointing out the utility of creatinine and cystatin C tests in evaluating the kidney functions during thyroid diseases, which are important community health problems. In this study, variations on levels of cystatin C and creatinine are compared, which were measured with hypothyroid and hyperthyroid patients before the treatment and euthyroid status after the treatment. In this study 31 hyperthyroid patients and 29 hypothyroid patients selected as samples, who were already diagnosed but not treated yet, and 29 healthy people as test sample. For hyperthyroid patients methymazol treatment applied and for hypothyroid patients L-thyroxine treatment applied and these are followed until otiroid status. FT3, FT4, TSH, cystatin C and creatinine tests are exercised two times, one at diagnosis phase and one after treatment when they reached euthyroid status. Evolution of cystatin C and creatinine levels against beginning level were compared. In hyperthyroid patients sample, the serum cystatin C levels at diagnosis stage were clearly higher than the test sample (p<0,0001). In the same sample serum creatinine levels were clearly lower than the test sample (p<0,0001). In hypothyroid patients sample the serum cystatin C levels at diagnosis stage were clearly lower than the test sample (p<0,0001). In the same sample, even the serum creatinine levels were higher than the test sample, statistically significant difference can not be determined (p>0,05). After hyperthyroid treatment, 23% decrease in sistatin C level on the average and 24% increase in creatin level on the average were determined. After hypothyroid treatment, 12% increase in cystatin C level on the average and 11% decrease in creatinine level on the average were determined. As a result of this study, "thyroid dysfunction affects the serum creatin and cystatin C levels significantly" conclusion was reached. According to these results; when cystatin C or creatinine is used as kidney function identifier, disruptive effects of thyroid dysfunction need to be taken into consideration. Knowledge of clinician about the effects of thyroid dysfunction on levels of serum cystatin C and creatinine is important to prevent from unnecessary investigations and costs.