What is a potential cause of hypercalcemia?

Hypercalcemia, which refers to elevated levels of calcium in the blood, can occur due to several underlying conditions, and one of the most notable causes is cancer. Specifically, certain cancers can lead to hypercalcemia through various mechanisms, such as the production of parathyroid hormone-related peptide (PTHrP), which mimics the action of parathyroid hormone and increases calcium release from bones. Additionally, certain tumors can cause bone metastasis that releases calcium into the bloodstream.

In contrast, hypertension and excessive vitamin B intake do not have a direct link to increased calcium levels in the body. While kidney stones can be a consequence of hypercalcemia, they are not a direct cause of the condition itself. Therefore, cancer stands out as a significant medical factor that can lead to an increase in calcium levels, making it the correct answer in this context.