Effect Of Hypo-and Euthyroid Status On Serum Cystatin C Levels-Original Article

Abstract

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.Conflict of interest:None declared.

Estimation of Glomerular Filtration Rate From Serum Cystatin C and Creatinine in Patients with Thyroid Dysfunction

“…In addition, cystatin C levels in our hypothyroid subjects were not below the reference range for the method applied, which is also consistent with several previous studies (13)(14)(15)(16). The low cystatin C levels seen in hypothyroidism are likely a result of the decreased overall metabolic activity and decreased cystatin C production due to low levels of thyroid hormones (13,15,16). However, studies that followed the effects of thyroid hormone replacement therapy on serum cystatin C report that changes in the levels of cystatin C in hypothyroidism are transient and that its levels increase after restoration of the euthyroid state (13)(14)(15)(16)(17).…”

“…In addition, cystatin C levels in our hypothyroid subjects were not below the reference range for the method applied, which is also consistent with several previous studies (13)(14)(15)(16). The low cystatin C levels seen in hypothyroidism are likely a result of the decreased overall metabolic activity and decreased cystatin C production due to low levels of thyroid hormones (13,15,16).…”

“…Studies on the effects of thyroid suppression therapy (11)(12)(13)(14)(15) and thyroid hormone replacement (11)(12)(13)(14)(15)(16) in patients with thyroid dysfunction have shown that serum creatinine levels change significantly during the treatment.…”

Cystatin C

“…Consistent with these properties, in our results, age, gender and BMI did not affect cystatin C levels as described previously. 16,17,26,27 When a renal injury occurs, cystatin C plasma levels increase. [23][24][25]27 Other conditions that may influence cystatin C values are thyroid illness, corticosteroid therapy and chronic viral infections, such as HIV infection.…”

“…A possible immune function in chronic viral infections has been described as well. [23][24][25][26] Cystatin C is freely filtered and completely reabsorbed and catabolized in the proximal renal tubules. Therefore, its urine concentration is minimal, and its blood concentration is constant.…”