Serum Cystatin C Concentrations in Patients with Graves’ Ophthalmopathy

Purpose: To evaluate the concentration of serum cystatin C (CysC) in patients with Graves’ ophthalmopathy (GO) and the usabilityof the serum CysC concentrations in the follow-up of the disease. Methods: Thirty patients with GO and 30 healthy age-matched volunteers were included in this cross-sectional study. GOwas diagnosed based on the European Group on Graves’ Orbitopathy consensus. Serum thyroid-stimulating hormone, freetriiodothyronine, free thyroxine, and CysC concentrations were measured in the participants. The serum CysC concentrationswere compared between patients with GO and controls. Patients with GO were subdivided into hyperthyroid and euthyroidpatients, and their serum CysC concentrations were compared. In addition, the CysC concentrations in hyperthyroid and euthyroidpatients with GO were compared separately with those of healthy subjects. Kruskal-Wallis test and Student’s t-testwere used for statistical evaluation. Results: The mean serum CysC concentrations in GO patients and controls were 1.04 ± 0.36 and 0.74 ± 0.09 mg/L, respectively. There was a statistically significant difference in the serum CysC concentrations between patients with GO and control subjects (p< 0.001). Fifteen patients had hyperthyroid status, and 15 patients had euthyroid status. The mean serum CysC concentrationsin hyperthyroid and euthyroid patients with GO were 1.35 ± 0.22 and 0.72 ± 0.13 mg/L, respectively. Serum CysC concentrationswere significantly higher in hyperthyroid patients than in euthyroid patients (p = 0.001). In addition, hyperthyroid patients hadsignificantly higher serum CysC concentrations than healthy subjects. Among patients with GO, 21 and nine had mild and moderate-to-severe GO, respectively. Active and inactive GO were observed in eight and 22 patients, respectively. Conclusions: The serum CysC concentrations in hyperthyroid patients were higher than those in healthy subjects. Moreover,hyperthyroid patients had higher serum CysC concentrations than euthyroid patients. Further studies with a larger samplesize are needed to confirm these results.