| Decreased intestinal absorption Starvation Absorption blocked by oral antacids or phosphate binders Parenteral alimentation with inadequate phosphate content Malabsorption syndrome, small bowel bypass Vitamin D–deficient and vitamin D–resistant osteomalacia Increased urinary excretion Hyperparathyroidism (primary or secondary) Hyperthyroidism Renal tubular defects with excessive phosphaturia (congenital, Fanconi syndrome induced by monoclonal gammopathy, heavy metal poisoning), alcohol use disorder Hypokalemic nephropathy Inadequately controlled diabetes mellitus Hypophosphatemic rickets Phosphaturic medications: intravenous iron, acetazolamide, tenofovir Phosphatonins of oncogenic osteomalacia (eg, FGF23 production) Transcellular shift of phosphorus Increased insulin secretion (ie, during refeeding) Anabolic steroids, estrogen, oral contraceptives, beta-adrenergic agonists, xanthine derivatives Hungry bone syndrome Acute respiratory alkalosis Salicylate poisoning Other Electrolyte abnormalities Hypercalcemia Hypomagnesemia Metabolic alkalosis Abnormal losses followed by inadequate repletion Diabetes mellitus with acidosis, particularly during aggressive therapy Recovery from starvation or prolonged catabolic state Chronic alcohol use disorder, particularly during restoration of nutrition; associated with hypomagnesemia Recovery from severe burns |