A 65 years old male diagnosed by biopsy a case of lung carcinoma, with paraneoplastic syndrome and increased PTH. Probable cause is-

Hypercalcemia is seen in squamous cell carcinoma of lung. The causal mechanism is the production of calcemic humoral substances, most impoantly parathyroid hormone-related protein ( PTHRP) . It has sone biological action similar to PTH. Several other factors like IL-1, TGF, TNF and dihydroxy vitamin D have also been implicated ( Pathologic basis of Disease, 8 th edition)