A 10-year-old boy has a fracture of femur. Biochemical evaluation revealed Hb 11.5 gm/dL and ESR 18 mm 1st hour. S. calcium 12.8 mg/dL, S.phosphorus 2.3 mg/ dL alkaline phosphate 28 KA units and blood urea 32 mg/dL. Which of the following is the most probable diagnosis in his case: