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 positive correlation 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.