Review Question - QID 4428

Urinary N-telopeptide is a marker of increased bone turnover and is a breakdown product of Type 1 collagen.

Increased serum alkaline phosphatase level and increased urinary markers of N-telopeptide, hydroxylproline, deoxypyridinoline indicate high bone turnover and can be seen in metabolic bone diseases such as Paget's disease.

von Schewelov et al. reviewed 160 patients that underwent total hip replacements and examined their urine specimens to see if N-telopeptide levels correlated to periprosthetic osteolysis. They found that n-telopeptide levels were 1/3 higher in the patients that had evidence of osteolysis. N-telopeptide release and annual wear were both associated with increased prevalence of osteolysis in the study.

Illustration A shows a radiograph of Pagets disease of the femur, an example of a condition where there is an increased level of N-telopeptide in the urine. Illustration B is a radiograph showing periprosthetic osteolysis, another condition where there is an increased level of N-telopeptide in the urine.

Incorrect Answers:
Answer 2: Increased urinary cAMP is found in Type 2 pseudohypoparathyroidism.
Answer 3: Phosphoethanolamine is found in the urine in patients with hypophosphatasia.
Answer 4: Bence Jones proteins are found in the urine of patients with multiple myeloma.
Answer 5: Bone sialoprotein (BSP) is a component of mineralized tissues such as bone, dentin, cementum and calcified cartilage.