Distinction between the common symptoms of the phosphate-depletion syndrome and glucocorticoid-induced disease

Severe hypophosphatemia. Pathophysiologic implications, clinical presentations, and treatment

We conducted this review to heighten the awareness and describe pathologic manifestations of hypophosphatemia. We present 3 cases of varied manifestations of hypophosphatemia where recognition was delayed. In certain settings, severe hypophosphatemia has significant morbidity and potential mortality. Appreciation of the pathophysiologic basis for organ dysfunction in severe hypophosphatemia should result in early recognition and treatment. We reviewed the English-language literature for reported cases and research studies dealing with pathophysiologic mechanisms subserving clinical manifestations. We observed that depletion of adenosine triphosphate (ATP) would explain most of the derangement noted in cellular functions. Phosphate plays a key role in the delivery of oxygen to the tissue. Lack of phosphate, therefore, leads to tissue hypoxia and hence disruption of cellular function. Severe hypophosphatemia becomes clinically significant when there is underlying phosphate depletion. Otherwise, short-term acute hypophosphatemia is not usually associated with any specific disorder. Chronic hypophosphatemia, on the other hand, results in hematologic, neuromuscular, and cardiovascular dysfunction, and unless corrected, the consequences can be grave. Most of the time hypophosphatemia results from renal loss of phosphate, diagnosed by a fractional secretion of phosphate > 5%. It is hard to provide precise estimates of how many patients are seen with hypophosphatemia annually at academic medical centers. This is complicated by use of chemistry panels that do not measure inorganic phosphate unless specifically ordered. This often leads to delay in correct diagnosis, and, therefore, additional delay in providing appropriate management. A high index of suspicion alone avoids the unnecessary withholding of treatment that can be life saving.

Musculoskeletal complications after renal transplantation: pathogenesis and treatment

Renal transplantation is associated with several abnormalities of function and structure of the musculoskeletal system. Some of these skeletal problems result from incomplete resolution of abnormalities of bone and mineral metabolism present at the time of transplantation. In this regard, persistent hyperparathyroidism, diabetes mellitus type 1, and accumulation of beta 2-microglobulin may lead to residual skeletal effects despite excellent function of the allograft. Persistent hyperparathyroidism may accelerate bone loss and increase the risk for osteonecrosis, as well as cause hypercalcemia and hypophosphatemia; some patients with severe hyperparathyroidism require parathyroid surgery. Osteonecrosis is the most debilitating skeletal complication after transplantation and frequently requires surgical therapy. Although osteomalacia associated with aluminum overload generally resolves after transplantation, bone complications due to dialysis amyloidosis and diabetes mellitus type 1 often fail to improve. Alternatively, skeletal abnormalities can be acquired after transplantation. Most of the new derangements of bone and mineral metabolism are due to the immunosuppressive medications. Toxic effects of glucocorticoids on bone contribute to the pathogenesis of osteonecrosis, increase the risk for fractures by decreasing cancellous bone mass and synthesis of bone matrix, and dampen the linear growth response in pediatric recipients. Whether cyclosporine independently causes appreciable toxic effects on bone metabolism is not yet clear, but use of this drug increases the prevalence of gout and dental problems. Osteonecrosis, osteopenia, and short stature remain important skeletal complications in recipients of renal allografts. Therapeutic efforts should be directed toward alleviating pretransplant bone disease and attenuating bone loss after transplantation.

Hypophosphatemia. Causes and clinical consequences

Severe hypophosphatemia (i.e., serum phosphorus concentration below 1 mg/dl) occurs infrequently in veterinary patients. It is most often associated with diabetic ketoacidosis in small animals. Phosphate is necessary for the production of 2,3 diphosphoglycerate (2,3-DPG) and adenosine triphosphate (ATP); both are important for normal cellular metabolism. Consequences of severe hypophosphatemia may include hemolytic anemia, seizures, altered mentation, cardiomyopathy, and skeletal muscle weakness. Parenteral phosphate therapy is necessary in most cases of severe hypophosphatemia.

Hypophosphatemia and respiratory failure: prolonged abnormal energy metabolism demonstrated by nuclear magnetic resonance spectroscopy

Hypophosphatemia has been shown to cause acute respiratory failure. The mechanism is believed to be due to decreased high-energy substrate availability at the cellular level leading to respiratory muscle dysfunction. However, direct measurement of these substrates has not been previously studied. A patient with hypophosphatemic respiratory failure is described in whom phosphocreatine and pH were continuously monitored using nuclear magnetic resonance spectroscopy. This revealed a defect in muscle metabolism that required several weeks to recover despite prompt correction of the serum phosphate level.

Adsorption of phosphate by aluminum hydroxycarbonate

Phosphate is specifically adsorbed by aluminum hydroxycarbonate by anion ligand exchange. IR analysis indicated that phosphate exchanged with specifically adsorbed carbonate. Adsorption is favored by low pH and is inversely related to particle size. Adsorption of phosphate decreases the rate of acid neutralization of aluminum hydroxycarbonate. The results are applied to the treatment of hyperphosphatemia and hypophosphatemia.