A 74-year-old woman has metastatic bone disease on x-ray. Which of the following mediators is least likely to be involved?: (A) interleukin-6 (IL-6), (B) ectopic parathyroid hormone (PTH), (C) tumor necrosis factor (TNF), (D) interleukin-1 (IL-1)
Answer is B. A whole host of locally produced hormones and cytokines, as well as ectopically produced hormones, are implicated in local osteoclastic hypercalcemia. Parathormone-related protein is often elevated in malignant hypercalcemia (with or without bony metastases), but ectopic PTH production in malignancy is quite rare.