O0056 MINERAL METABOLISM AND RISK OF OSTEOPOROSIS IN OBESE CHILDREN

Abstract

Introduction: It is well known that there is relation between obesity and altered body metabolism. Many previous studies prove such relation concerning lipid metabolism and its role in developing atherosclerosis, but little attention was directed to study calcium homeostasis and mineral metabolism with risk of developing osteoporosis in these patients.So, we carried out this investigation to determine possible relationships of mineral metabolism and risk of osteoporosis with obesity in children. Methods: Blood levels of calcium (Ca), phosphorous (P), alkaline phosphatase (AP), osteocalxcin (OC), parathyroid hormone (PTH), calcitonin (CT), 25 - hydroxy vitamin D3 (25 OHD3), 1,25 dihydroxy vitamin D3 (1,25 (OH)2D3 ) and urinary excretion of Ca (Ca /Cr), P (Tm P/GFR), hydoxy proline (OH-P/Cr) and cyclic AMP (cAMP/ GFR) were determined in a sample of 20 obese children aged 9–12 years compared to 15 controls of the same age range. Results: Body mass index (BMI) averaged 33.2 ± 3.9 kg/m2 in the obese and 20.8 ± 2.8 kg/m2 in the control group (P<0.001). Whereas mean serum calcium and phosphorous were the same in the two groups, mean serum (PTH), (AP), (OC), (CT) and (1,25 (OH)2D3 ) were significantly higher and mean serum (25 OHD3 ) was significantly lower in the obese children than in the control group with P<0.001. Mean urinary (Ca) and (P) were significantly lower (P<0.005 and <0.05 respectively) and mean urinary (OH-P) and cAMP) were significantly higher in the obese than non obese individuals with P<0.005 and <0.001 respectively. There was a significant positive correlation between BMI and urinary cAMP (r = 0.48, P<0.01) and serum PTH (r = 0.69,P<0.01) in the two groups. Conclusion: The results provide evidence that alteration of mineral metabolism in obese children is characterized by secondary hyperparathyroidism which is associated with enhanced bone resorption and increased risk of osteoporosis.