DECREASED LUMBAR SPINE BONE MASS AND LOW BONE TURNOVER IN CHILDREN AND ADOLESCENTS WITH INSULIN-DEPENDENT DIABETES-MELLITUS FOLLOWED LONGITUDINALLY

The effects of insulin dependent diabetes mellitus (IDDM) on bone meta bolism are still not web defined. We evaluated total bone mineral cont ent (TBMC) and bone mineral density (BMD) at the lumbar spine and femo ral neck using dual X-ray absorptiometry in 26 IDDM children (15 M, 11 F) with a mean chronological age of 12.1 +/- 3.1 yr (range 7.1-14.2 y r), Duration of diabetes was 4.3 +/- 2.9 yr, with a mean glycosylated hemoglobin of 9.2 +/- 0,4%, BMD and TBMC standard deviation scores (Z- scores) were determined by comparing our results to controls matched f or age, sex and pubertal status. BMD and bone formation and resorption markers were determined at the beginning of the study and after one y ear of follow up, Mean lumbar spine Z-score was -1.06 +/- 0,2, with ne gative values in 24 of 26 children (92.6%); 14/26 patients (53.8%) had a lumbar spine Z-score >1.0 SD below the mean. Mean lumbar spine Z-sc ore remained unchanged after one year of follow up (-1,02 +/- 0,3), No significant differences were obtained in femoral neck BMD or TBMC bet ween groups. No correlation was observed between lumbar spine BMD Z-sc ores and duration of IDDM or degree of diabetes control, as assessed b y the mean glycosylated hemoglobin. Daily urinary calcium excretion wa s elevated in our patients initially and after one year of follow up; however, no correlation was obtained between lumbar spine BMD and 24 h urinary calcium excretion, Carboxy-terminal propeptide of type 1 coll agen values and levels of urinary cross-linked N-telopeptides of type 1 collagen in the diabetic children were significantly lower than thos e of the matched controls, Osteoblastic activity as assessed by serum osteocalcin and by the carboxy-terminal propeptide of type I collagen and bone resorption as measured by crosslinked N-telopeptides of type I collagen did not correlate with the lumbar spine Z-scores, When IDDM patients were subdivided into males and females and into children wit h more than or less than 2 yr duration of diabetes since diagnosis, no differences between groups were found, These results suggest that ins ulin dependent diabetes in children is associated with low bone turnov er resulting in a deficit in bone mass which may be manifested as oste openia in the growing bone. This defect is already present in trabecul ar bone early on in the disease and seems not to be related to glycemi c control.