Which of the following electrolytes is NOT abnormal in tumor lysis syndrome?

In the context of tumor lysis syndrome, hyperkalemia, hypocalcemia, and hyperphosphatemia are expected electrolyte abnormalities due to the rapid breakdown of tumor cells releasing their intracellular contents into the bloodstream.

Hyperkalemia arises from the massive release of potassium, which is abundant within cells. Hypocalcemia can occur as a result of an increase in phosphate levels that binds calcium, leading to a decreased serum calcium concentration. Hyperphosphatemia is a direct consequence of the release of phosphate from lysed tumor cells.

Hypomagnesemia, however, is not a typical feature of tumor lysis syndrome. Tumor lysis syndrome mainly leads to disturbances in potassium, calcium, and phosphate levels. Therefore, hypomagnesemia is not a standard finding in the disorder, which makes it the correct choice in identifying the electrolyte that is NOT abnormal in this syndrome. Understanding the pathophysiology of tumor lysis syndrome clarifies why these particular electrolyte imbalances occur and reinforces the knowledge of their expected changes during the syndrome.