FGF23 and hyperparathyroidism: After access to doxycycline-containing water for 6.5 weeks, a time point when proteinuria, defective renal function, and hyperparathyroidism with elevated FGF23 and low 1,25-vitamin D are present, mice were treated once with vehicle or SK-124 and euthanized 4 hours later (Figure 9A), a time point determined based on initial assessment of the kinetics of SK-124–induced Cyp27b1 induction and serum 1,25-vitamin D increases in control and CKD mice (Supplemental Figure 15).