Effect Of Hypo−and Euthyroid Status On Serum Cystatin C Levels

OBJECTIVE The aim of this study was to investigate the effect of hypo- and euthyroid status on serum cystatin C (CysC) levels in children and to explore whether CysC can be used as a marker of the thyroid status. METHODS Twenty five patients with hypothyroidism (10M, 15F; mean age:8.7±4.9 years) and 21 healhty age-matched controls (9M, 12F; mean age: 9.7±5.0 years) were included in this study. Serum thyrotropin (TSH), free thyroxine (fT4), serum CysC and creatinine levels were studied in patients with hypothyroidism twice, i.e. in the euthyroid (on L-T4) and hypothyroid state, and in controls. RESULTS No significant differences in creatinine, glomerular filtration rate (GFR) and CysC levels were observed between the study group in the euthyroid status and the control group. CysC (mg/dL) level was found to be lower in the hypothyroid status(0.6±0.1) than in the euthyroid status (0.66±0.1) (p=0.01). In hypothyroid status, CysC levels showed a positive correlation with GFR (r=0.463, p=0.02) and GFR had positivecorrelation with fT4 (r=0.563, p=0.012). CONCLUSIONS We demonstrated a significant effect of thyroid dysfunction on CysC levels, but the changes in serum CysC levels in hypo- and euthyroid status did not exceed the reference interval. It may be concluded that serum CysC levels have limited use in evaluating the peripheral effects of thyroid hormones.