Paradoxical Changes in Cystatin C and Serum Creatinine in Patients with Hypo- and Hyperthyroidism

In the ongoing search for improved serum markers of impaired renal function (1), the low-molecular-weight protein cystatin C has been advocated as a promising and probably superior alternative to creatinine when used to assess glomerular filtration rate (GFR) (2)(3). Cystatin C possesses most of the properties of an ideal GFR test in that it is produced by all nucleated cells at an apparently constant rate, is freely filtered at the glomerulus,...