FGF23 and secondary hyperparathyroidism: In comparison to healthy controls, previous studies showed that mice fed a 0.2% adenine diet exhibited biochemistries typical to CKD such as hyperphosphatemia, hypocalcemia, secondary hyperparathyroidism, increased blood urea nitrogen (BUN), and FGF23 induction, which are enhanced with the duration of treatment, as well as associated with bone porosity during chronic adenine administration (15).