Endocrine Abstracts

Bone turnover markers (BTMs) may have a role in assessing bone turnover and response to intervention in Paget’s disease. We examined the clinical utility of bone turnover markers at diagnosis through analysis of our database of patients with radiographically confirmed Paget’s disease.

We identified 36 patients (20 men); mean age at diagnosis was 71.6 years (range 54–84). Radionuclide imaging identified that 64% had polyostotic disease, with no gender difference. At diagnosis, all patients had estimation of ionised calcium, total alkaline phosphatase (total ALP), parathyroid hormone (PTH), and 25-hydroxyvitamin D (25OHD). The following BTMs were measured in serum in the fasting state: bone-specific alkaline phosphatase (bone ALP), procollagen type I N-propeptide (PINP), intact osteocalcin (OC(1–49)), and C-terminal cross-linking telopeptide (CTX). Fasting spot urine was collected for measurement of N-terminal cross-linking telopeptide (NTX).

Serum 25OHD was <50 nmol/l in 36%; 2/36 (6%) had raised PTH; none were hypercalcaemic. The prevalence of abnormal BTMs was as follows: total ALP (67%); bone ALP (67%); PINP (36%); OC(1–49) (36%); CTX (31%); and NTX (44%). Total ALP correlated significantly with bone ALP (r=0.48, P=0.016), with OC(1–49) (r=0.47, P=0.03), with PINP (r=0.73, P<0.0001), and with NTX (r=0.59, P=0.006) but not with CTX. Total ALP was significantly higher in those with polyostotic disease at diagnosis (P=0.019) as was NTX (P=0.02) but not other BTMs. Fourteen patients were screened for the Q3STM1 mutation; two were positive. One of these patients had the only raised osteocalcin identified; otherwise there were no differences between these and the Q3STM1-negative cohort.

While BTMs are not needed for the diagnosis of Paget’s disease, they are helpful is quantifying the degree of activity and in assessing the response to bisphosphonate therapy. Total ALP has similar utility to the newer BTMs, and would be a cheaper substitute assuming that the patient did not have concomitant hepatobilary disease.