Step 1: To answer an except question, recall the actual toolkit for lowering a high serum calcium and then spot the intruder.
Step 2: The backbone is volume repletion with saline followed by a loop diuretic to drive calcium out in the urine. Bisphosphonates shut down osteoclast-driven bone breakdown, and calcitonin gives a quick early drop.
Step 3: Beyond these, oral phosphate binds calcium, and glucocorticoids (steroids) are effective when excess vitamin D or granulomatous disease drives the calcium up. Dialysis is reserved for severe or renal cases. Thus steroids, bisphosphonates and phosphate all belong on the list.
Step 4: Strontium, in the form of strontium ranelate, is a bone-building agent for osteoporosis and plays no part in treating hypercalcemia, so it is the odd one out.
\[\boxed{\text{Strontium}}\]