CYP27B1 and hypophosphatemia: Hypophosphatemia, defined as serum phosphate below 2.5 mg/dL, arises from disrupted homeostasis involving intricate feedback among parathyroid hormone (PTH), vitamin D, and FGF-23, where low phosphate normally stimulates CYP27B1 to enhance absorption via increased 1,25-dihydroxyvitamin D, while PTH (stimulated by low calcium) provides additional regulation but is suppressed by hypophosphatemia, but elevated FGF-23 counters this by promoting phosphaturia and inhibiting 1,25 Vit D synthesis [13-15].