CST3 and Polydipsia: Our findings that chronic STD-Li treatment resulted in significant polyuria and polydipsia (characteristic features of NDI) (Figure 2), and in elevated blood levels of creatinine and cystatin C (markers of abnormal renal function; Figure 3 and Figure 4) are in agreement with the strong evidence that long-term Li treatment is associated with renal function abnormalities [30,31,33].