Which condition is most commonly associated with a high level of serum calcium due to parathyroid hormone related peptide?

The condition that is most commonly associated with a high level of serum calcium due to parathyroid hormone-related peptide (PTHrP) is squamous cell lung carcinoma. This type of lung cancer is known for producing PTHrP, which mimics the action of parathyroid hormone and leads to hypercalcemia, often seen in patients with this malignancy.

In squamous cell lung carcinoma, the increased levels of PTHrP cause increased reabsorption of calcium from the bones and kidneys, as well as increased absorption of calcium from the intestine, resulting in elevated serum calcium levels. This paraneoplastic syndrome can lead to symptoms associated with hypercalcemia, such as weakness, confusion, and kidney stones.

Other malignancies, while potentially leading to hypercalcemia, do so via different mechanisms. For instance, renal cell carcinoma may also cause hypercalcemia, but it is generally related to osteolytic metastasis rather than the production of PTHrP. Breast cancer can cause hypercalcemia due to skeletal metastases as well as through osteolytic lesions, but its relation to PTHrP is less significant in comparison to squamous cell lung carcinoma. Prostate cancer typically does not produce PTHrP