Hyperfosfatemie

Hyperphosphatemia, also known as hyperfosfatemie, is a condition characterized by an elevated level of phosphate in the blood. In adults, it is generally defined as a serum phosphate concentration above about 1.5 mmol/L (approximately 4.5 mg/dL). It is most commonly seen in chronic kidney disease and end-stage kidney failure, where renal excretion of phosphate is impaired. Other causes include excessive phosphate intake, rapid cell breakdown (such as tumor lysis syndrome or rhabdomyolysis), vitamin D intoxication, hypoparathyroidism, and certain medications or conditions that reduce phosphate clearance or promote shifts of phosphate into the extracellular space.

Pathophysiology typically involves an imbalance between phosphate intake, cellular distribution, and renal excretion. In kidney disease, reduced filtration leads to phosphate accumulation. The excess phosphate can bind calcium, contributing to hypocalcemia and secondary hyperparathyroidism. Regulators such as fibroblast growth factor 23 (FGF23) and parathyroid hormone (PTH) adjust intestinal absorption and renal handling of phosphate, but their effects are limited when kidney function is impaired. Chronic hyperphosphatemia is linked to vascular and soft tissue calcification, contributing to cardiovascular risk and bone-mineral disorders in kidney disease.

Clinical features are often absent until phosphate levels are markedly elevated or complications arise. Symptoms may relate to hypocalcemia (tingling, cramps) or to calcifications in vessels and soft tissues. Diagnosis relies on measuring serum phosphate and assessing related parameters such as calcium, PTH, vitamin D, and kidney function, along with evaluation for underlying causes.

Management focuses on treating the underlying cause, restricting dietary phosphate intake, and using phosphate binders (calcium-based or non-calcium-based) with meals. In dialysis-dependent patients, optimization of dialysis and adjustment of vitamin D analogs and PTH-directed therapies are common. Severe hyperphosphatemia or calciphylaxis may require more aggressive interventions. Prognosis is closely tied to the presence and severity of kidney disease and associated vascular calcification.