This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lung Tumor, Subject name: Pathology
A 65-year-old male diagnosed by biopsy a case of squamous cell carcinoma of lung, has very high serum calcium levels. Probable cause is? 
Select and explain. 
A. Parathyroid hormone, B. Parathyroid hormone-related peptide, C. Calcitonin, D. Calcitonin-related peptide
B: Parathyroid hormone-related peptide
Answer: B: Parathyroid hormone-related peptide 
Explanation: Paraneoplastic syndromes The most impoant mechanism is the synthesis of a parathyroid hormone-related protein (PTHrP) by tumor cells (Commonly in Squamous cell carcinoma) leading to Hypercalcaemia.