<prompt> 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?Parathyroid hormoneParathyroid hormone-related peptideCalcitoninCalcitonin-related peptide  <response>: 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. 