Fricker Manuel, Wiesli Peter, Brändle Michael, Schwegler Beat, Schmid Christoph
Department of Internal Medicine, Division of Endocrinology and Diabetes, University Hospital of Zurich, Zurich, Switzerland.
Kidney Int. 2003 May;63(5):1944-7. doi: 10.1046/j.1523-1755.2003.00925.x.
Serum cystatin C (CysC) is a novel marker for kidney function that has been claimed to be superior to serum creatinine. Thyroid dysfunction may alter creatinine, which has been found to be increased in hypothyroidism and decreased in hyperthyroidism. This study was performed to evaluate whether changes in CysC and creatinine are parallel during the treatment of hypo- and hyperthyroidism, respectively.
Prospective case series of 22 consecutively referred patients with thyroid dysfunction. Creatinine and CysC were determined at the time of diagnosis of hypo- and hyperthyroidism, and when free thyroxine (fT4) returned into the normal range. Hypothyroid patients were treated with levothyroxine. Hyperthyroid patients were treated with antithyroid drugs, surgery, or radioiodine.
Nine patients with hypothyroidism and 13 patients with hyperthyroidism were included. In patients with hypothyroidism mean fT4 (+/-SD) was 4.9 +/- 2.5 pmol/L (reference, 12 to 22) at diagnosis and increased to 16.6 +/- 3.6 pmol/L when patients were treated with levothyroxine. Creatinine decreased from 86 +/- 13 micromol/L (reference, 70 to 105) in the hypothyroid state to 76 +/- 16 micromol/L when fT4 normalized (P = 0.062), whereas CysC increased from 0.84 +/- 0.17 mg/L (reference, 0.63 to 1.33) to 1.1 +/- 0.28 mg/L (P < 0.001). In patients with hyperthyroidism, mean fT4 was 54.6 +/- 22.7 pmol/L (reference, 12 to 22) at diagnosis and decreased to 15.8 +/- 3.6 pmol/L following treatment with antithyroid drugs, thyroid surgery, or radioiodine. Creatinine increased from 67 +/- 15 micromol/L at diagnosis of hyperthyroidism to 75 +/- 9 micromol/L when fT4 normalized (P = 0.004), whereas CysC declined from 1.32 +/- 0.17 mg/L to 0.95 +/- 0.19 mg/L (P < 0.001).
Thyroid dysfunction has a major impact on CysC levels. Therefore, thyroid function has to be considered when CysC is used as a marker of kidney function. In contrast to creatinine concentrations, CysC levels are lower in the hypothyroid and higher in the hyperthyroid state as compared with the euthyroid state.
血清胱抑素C（CysC）是一种新的肾功能标志物，据称优于血清肌酐。甲状腺功能障碍可能会改变肌酐水平，已发现甲状腺功能减退时肌酐水平升高，甲状腺功能亢进时肌酐水平降低。本研究旨在评估在甲状腺功能减退和亢进的治疗过程中，CysC和肌酐的变化是否平行。
对22例连续转诊的甲状腺功能障碍患者进行前瞻性病例系列研究。在诊断甲状腺功能减退和亢进时以及游离甲状腺素（fT4）恢复到正常范围时测定肌酐和CysC。甲状腺功能减退患者接受左甲状腺素治疗。甲状腺功能亢进患者接受抗甲状腺药物、手术或放射性碘治疗。
纳入9例甲状腺功能减退患者和13例甲状腺功能亢进患者。甲状腺功能减退患者诊断时平均fT4（±标准差）为4.9±2.5 pmol/L（参考范围，12至22），接受左甲状腺素治疗后升至16.6±3.6 pmol/L。肌酐水平从甲状腺功能减退状态时的86±13 μmol/L（参考范围，70至105）降至fT4正常时的76±16 μmol/L（P = 0.062），而CysC从0.84±0.17 mg/L（参考范围，0.63至1.33）升至1.1±0.28 mg/L（P < 0.001）。甲状腺功能亢进患者诊断时平均fT4为54.6±22.7 pmol/L（参考范围，12至22），接受抗甲状腺药物、甲状腺手术或放射性碘治疗后降至15.8±3.6 pmol/L。肌酐水平从甲状腺功能亢进诊断时的67±15 μmol/L升至fT4正常时的75±9 μmol/L（P = 0.004），而CysC从1.32±0.17 mg/L降至0.95±0.19 mg/L（P < 0.001）。
甲状腺功能障碍对CysC水平有重大影响。因此，在将CysC用作肾功能标志物时必须考虑甲状腺功能。与肌酐浓度不同，与甲状腺功能正常状态相比，甲状腺功能减退时CysC水平较低，甲状腺功能亢进时CysC水平较高。
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