This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which of the following describes humoral hypercalcemia of malignancy (HHM)? 
Select and explain. 
A. The rise in calcium levels due to PTH-rP, B. Paraneoplastic Calcitonin Production, C. Vitamin D Hypervitaminosis, D. Parafollicular C-cell proliferation of Thyroid Gland
A: The rise in calcium levels due to PTH-rP
Answer: A: The rise in calcium levels due to PTH-rP 
Explanation: The rise in calcium levels due to PTH-rP is termed humoral hypercalcemia of malignancy (HHM). A common consequence of some cancers can be increased levels of calcium (hypercalcemia) with secretion of PTH-related peptide (PTH-rP). PTH-rP has significant homology with PTH, but only in the amino-terminal 13 amino acids, which make up the receptor-binding region. Because PTH-rP is not secreted by the parathyroid glands, hypercalcemia produces no feedback regulation of its production. Cancers usually associated with HHM include breast and lung cancers and multiple myeloma. Ref: Kerr J. (2012). Chapter 13. Connective Tissue and Bone. In L.W. Janson, M.E. Tischler (Eds), The Big Picture: Medical Biochemistry.