Which of the following is NOT a cause of hypocalcemia?

Hypoparathyroidism, hypomagnesemia, and pancreatitis are all conditions that can lead to hypocalcemia. Hypoparathyroidism results in inadequate secretion of parathyroid hormone (PTH), which is essential for maintaining calcium levels in the blood. A deficiency in PTH leads to decreased calcium reabsorption in the kidneys and increased calcium loss in the urine, contributing to lower serum calcium levels.

Hypomagnesemia can also cause hypocalcemia, as magnesium is necessary for the secretion of PTH. Low levels of magnesium can result in impaired PTH secretion and action, leading to decreased calcium levels.

Pancreatitis can lead to hypocalcemia through the precipitation of calcium soaps in the abdominal cavity as fat necrosis occurs. This can significantly decrease circulating calcium levels.

In contrast, hyperparathyroidism is characterized by excessive secretion of PTH, which typically increases serum calcium levels rather than decreasing them. The condition promotes bone resorption, increases intestinal absorption of calcium, and reduces renal excretion of calcium, all contributing to elevated calcium levels. Therefore, hyperparathyroidism is not a cause of hypocalcemia but rather contributes to hypercalcemia.