C H A N G E I N T O T A L B O D Y W A T E R A S A P R E D I C T I V E T O O L F O R G R O W T H H O R M O N E T R E A T M E N T R E S P O N S E Introduction In pediatric endocrinology short stature is a frequently seen problem. Children with short stature due to growth hormone deficiency (GHD) or due to be born small for gestational age (SGA) are indicated for growth hormone treatment. However, not all children seem to benefit from this treatment and it is unclear how to predict whether a child will have an adequate or inadequate response to growth hormone therapy. Short stature as a result of GHD has an incidence of 1:3500 and is the original indi-‐ cation for treatment with recombinant human growth hormone (rhGH) in child-‐ hood. According to the Dutch rules at least two stimulation tests (for example clonidine and arginine test) with an increase of growth hormone below 20 mU/l are needed to confirm the diagnosis of GHD and to obtain an indication for rhGH treat-‐ ment1. Despite the results of the stimulation tests, the individual responses to treatment with rhGH vary widely. The second well-‐defined indication for rhGH treatment2 is restricted to those infants with birth weight and/or length of at least 2 SD below the mean for gestational age, and without catch-‐up growth before the age of 4 years (SGA)1. They do not need a stimulation test and a normal value of insuline-‐like growth factor (IGF1) is no contraindication for treatment. Most of the SGA children have a spontaneous catch-‐up growth in the first 2 years of life, but 1 out of 10 subjects remains of short stature during childhood and seems to benefit from treatment with rhGH. The mechanisms that are involved in this catch-‐up growth in SGA children are unknown2 and none of the endocrine parameters seem to have any predictive value. Already at an early age both the GHD and the SGA children show abnormalities in body composition3. While GHD children show an increased total body fat, SGA chil-‐ dren show a reduced body fat percentage4,5. Treatment with rhGH in adults causes a shift in body composition towards an increase in fat-‐free mass (FFM)6. In children with GHD the same effect was found in several studies during treatment with rhGH3,7-‐11. It is also proven that a shift in body composition is already present after 6 weeks of treatment8-‐12. In the study of Hoos et al.13 it is shown that the increase in FFM, measured with the Deuterium dilution method after 6 weeks of treatment, is a valuable tool for distinction between good and poor responders on growth meas-‐ ured after one year of treatment in children diagnosed with GHD. A comparable effect in SGA children is not described in literature yet. Objectives Based on the above mentioned results a Dutch nationwide study was performed to investigate whether the findings of the study of Hoos et al.13 could be confirmed in a larger cohort of children indicated for rhGH treatment. A second objective of this 45
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