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While bone mineral density of the forearm is not decreased in pediatric renal transplant recipients, bone strength in relation to muscular force is reduced. This alteration may contribute to the increased propensity for fractures in these patients.

Sirs,We read with great interest the article of Foster et al.[1] on risk factors for glucorticoid-induced obesity in children with steroid-sensitive nephrotic syndrome (SSNS). The prevalence of obesity in patients with remote SSNS was high with 20%, however, not significantly different from the prevalence in the reference group. We have recently reported a comprehensive long-term study on 42 adults treated for childhood SSNS, providing also a detailed analysis of growth [2]. The median BMI was 23 kg/m 2 ; in five women and three men the BMI was >25, and only one female was obese, with a BMI of 31.4. No correlation was found between height and weight in adulthood and the cumulative prednisone dose or duration of prednisone administration. The epidemic of being overweight and obese appears to be more prevalent in the US than in some European countries. We suggest to add to the conclusion of Foster's report that the prevalence of persistent obesity in children with SSNS is also correlated with the local prevalence or epidemic of obesity in the healthy reference group.Also, other clinical endpoints seem to differ in various geographical areas. Hegarty et al.[3] reported a high prevalence of bone fractures in adults treated with steroids for childhood SSNS in the UK: Of the 24 male and 10 female subjects, 19 (79.2%) and 3 (30%), respectively, had suffered a total of 43 self-reported fractures. In contrast, only 2 (5%) of the 42 patients in our study had sustained a single bone fracture although our patients were not given calcium or vitamin D supplements.We propose that the long-term outcome and clinical endpoints in steroid-sensitive idiopathic nephrotic syndrome not only depend on treatment regimens and therapy responsiveness, but also on regional circumstances, lifestyles and living conditions. References 1. Foster BJ, Shults J, Zemel BS, Leonard MB (2006) Risk factors for glucocorticoid-induced obesity in children with steroid-sensitive nephrotic syndrome. Pediatr Nephrol 21:973-980 2. Rüth E-M, Kemper MJ, Leumann EP, Laube GF, Neuhaus TJ (2005) Children with steroid-sensitive nephrotic syndrome come of age: long-term outcome. J Pediatr 147:202-207 3. Hegarty J, Mughal MZ, Adams J, Webb NJA (2005) Reduced bone mineral density in adults treated with high-dose corticosteroids for childhood nephrotic syndrome.

The post-transplant bone disease of the peripheral skeleton in pediatric renal transplant recipients is characterized by an inadequately thin bone cortex in relation to muscular force. A major hormonal modulator of periosteal growth is the insulin-like growth factor (IGF)/IGF binding protein (IGFBP) system. We therefore hypothesized that the reduced cortical thickness in these patients may be due to functional IGF deficiency. To test this hypothesis, we investigated 55 patients (mean estimated glomerular filtration rate 86.3 +/- 30.0 ml/min/1.73 m(2)) in a cross-sectional study. Parameters of macroscopic bone architecture and forearm muscle size were analyzed by peripheral quantitative computed tomography (pQCT), and serum IGF/IGFBP system components were measured by specific radioimmunoassays. The mean (+/- standard deviation) standardized serum IGF-I (0.20 +/- 1.16 score) level was normal, while the mean IGF-II (1.16 +/- 0.11 score) level was significantly elevated. Serum IGFBP-1 and IGFBP-2 levels were not altered, whereas the IGFBP-3 (1.34 +/- 0.15 score) level was significantly increased. The serum IGFBP-4 level was slightly elevated (by 11%), the IGFBP-6 level was markedly (2.3-fold) elevated, while the IGFBP-5 level was comparable to that of the control. The respective age-adjusted cortical thickness at both the proximal (r = 0.407, P < 0.005) and distal (r = 0.383, P < 0.01) forearm was positively correlated with the standardized serum IGF-I level. In conclusion, the serum IGF/IGFBP system in pediatric renal transplant recipients is characterized by an increase in the levels of the inhibitory IGFBPs, IGFBP-3, -4 and -6, resulting in a functional IGF deficiency. The positive correlation of IGF-I with cortical thickness underlines the importance of this hormonal system in the modeling of bone, particularly periosteal growth.