<prompt> A patient presents with low serum calcium, high phosphorus and elevated PTH. Which of the following investigations is least contributory to establish a diagnosis:Vitamin D levelsSerum creatinine levelsCyclic AMP response to PTHUrine myoglobin  <response>: Answer is A Vitamin D levels: Vitamin D deficiency is associated with hypophosphatemia and not hyperphosphatemia Renal failure t serum creatinine, Pseudohypoparathyroidism J-CAMP response to PTH and increased urinary myoglobin crush syndrome; tissue injury may all be associated with combination of hypocalcemia, hyperphosphatemia and elevated PTH levels 