However, serum cystatin C is limited in the following two ways: 1) it is affected by diabetes, high levels of corticosteroids, hyperthyroidism, inflammation, hyperbilirubinemia, and hypertriglyceridemia [53]; 2) when GFR reaches < 15 mL/min/1.73 m2, the increase in serum cystatin C slows and levels off at 5-6 mg/L [54]. Here, CST3 is linked to hyperthyroidism.