Which electrolyte imbalance is NOT associated with tumor lysis syndrome?

Tumor lysis syndrome (TLS) is characterized by the rapid release of intracellular contents into the bloodstream after the breakdown of tumor cells, often following chemotherapy. This can lead to several distinct electrolyte imbalances due to the release of metabolic byproducts from the destruction of cancerous cells.

Hyperkalemia refers to an excess of potassium in the blood, which occurs as potassium is released from lysed cells. Hyperphosphatemia results from the release of phosphate, another intracellular component, into the bloodstream upon tumor cell lysis. Hypocalcemia can occur due to the precipitate formation that arises from elevated phosphates binding with calcium, which can lower calcium levels in the bloodstream.

In contrast, hyponatremia, or low sodium levels, is not typically associated with tumor lysis syndrome. TLS primarily causes imbalances in potassium, phosphate, and calcium due to the cellular breakdown and does not generally include sodium imbalance as a direct result. Therefore, hyponatremia is the electrolyte imbalance that is least expected in the context of tumor lysis syndrome. This understanding highlights the specific biochemical changes that occur during TLS and reinforces the importance of monitoring these electrolytes in at-risk patients.