The primary objective of this study is to evaluate the safety use of ETV and TDF after at least 144 weeks of treatment in terms of the effects of renal tubular function as determined by (1) 24 hours Urine phosphate (wasting is >1200 mg daily); (2) 24 hours β2-microglobulinuria (NL β2-microglobulin level, <1 mg daily); (3) fractional excretion of uric acid, and (4) fractional tubular reabsorption of phosphorus.