RESUMO
Aim: The aim of this study was to determine the relationship of biochemical markers of bone metabolism in patients with ankylosing spondylitis [AS] with bone mineral density, disease duration and activity of the disease. Subjects and 20 AS patients were studied. 17 were males and 3 were females. The mean age was 33.6 +/- 5.42 years. The mean disease duration was 17.5 +/- 7.82 years. Fifteen normal controls with matched age and sex were included. All subjects were subjected to full clinical examination. Radiological assessment included radiographs of pelvis and lumbar spine. Syndesmophytes score was obtained. Estimation of serum concentration of Ca, Ph, alkaline phosphatase, albumin, ESR, CRP and osteocalcin was done. Determination of urinary deoxypyridinoline [DPD] was made. Bone mineral density [BMD] was assessed for lumbar spine and left femoral neck using dual energy X-ray absorptiometry [DEXA]. Lumbar spine showed osteopenia in 45% of AS patients and osteoporosis in 30%, while 55% of patients had osteopenia and 25% had osteoporosis in the femoral neck. Biochemical data showed normal values of serum calcium, phosphorus and creatinine. The mean serum alkaline phosphatase was higher in AS patients [mean11.125 +/- 4.7845 units] than in control subjects [mean was 6.7667 +/- 2.0777 units]. The serum osteocalcin levels were significantly lower in AS [9.6000 +/- 2.700 ng/ml] than in control subjects [14.500 +/- 4.0 ng/ml]. The mean urinary excretion of DPD to creatinine ratio was significantly higher [P<0.05] in AS patients [8.295 +/- 4.5494] than in control subjects [4.5667 +/- 0.7743].Conclusions: In AS patients, osteoporosis and osteopenia are frequent and observed in early stages of the disease. This decrease of bone mass is due to both reduction of bone formation and increased bone resorption. Only the BMD of lumbar spine was positively correlated with disease duration. The biochemical markers of bone turnover were positively correlated with markers of inflammation [ESR and CRP]. A negative correlation was found between makers of bone resorption and BMD of lumbar spine and femoral neck