Which laboratory finding is characteristic of Paget disease of bone?

Paget disease of bone is characterized by abnormal and excessive bone remodeling, which leads to the formation of structurally abnormal bone. One of the hallmark laboratory findings in patients with Paget's disease is elevated alkaline phosphatase levels. Alkaline phosphatase is an enzyme that is found in several tissues throughout the body, but it is particularly concentrated in the liver, bones, kidneys, and bile ducts.

In the case of Paget disease, the elevated levels of alkaline phosphatase reflect increased osteoblastic activity, which is the activity of bone-forming cells that are trying to keep up with the high rate of bone turnover caused by the disease. This increase can be much higher than normal, indicating that the bone remodeling process is excessively active.

Other options present different scenarios: low calcium levels are not characteristic of Paget's disease, as most patients maintain normal serum calcium due to compensatory mechanisms. Increased serum phosphate is also not typical for Paget disease, as the phosphate levels usually remain stable or are only altered in specific related disorders. While vitamin D levels may vary among individuals, the disease itself does not specifically cause a decrease in vitamin D levels, which can result from a range of different factors not directly related to Paget's