B

Multiple myeloma produces purely lytic bone lesions with little osteoblastic activity, so serum alkaline phosphatase (ALP) is usually normal, unlike the marked ALP rises seen in disorders with high bone-formation rates such as Paget’s disease, osteomalacia and the high-turnover state of hyperthyroidism [Annibali, 2021, PMID 33304804; Garnero, 1994, PMID 8157727].