BMI z-score as a prognostic factor for height velocity in children treated with recombinant human growth hormone due to idiopathic growth hormone deficiency

PurposeGrowth hormone deficiency (GHD) causes growth disturbances during childhood. The most recommended treatment of GHD is the administration of recombinant human growth hormone (rhGH). Recent studies have proved that well-nourished GHD children respond better to rhGH therapy compared to undernourished individuals. The aim of this study was to analyze nutritional status along with height velocity in GHD children during the first two years of rhGH therapy, and to estimate the optimal BMI z-score range in which these children achieve the best growth results.MethodsThis retrospective analysis included 80 prepubertal idiopathic GHD children treated with rhGH. Anthropometric data were obtained from medical records made at an initial visit and then follow-up visits after 12 and 24 months of treatment. The body mass index (BMI) was calculated and standardized into z-score, basing on Cole's LMS method. Then, the BMI z-score was analyzed in relation to the parameters of growth response.ResultsThe higher the BMI z-score at treatment entry, the greater the increase in height during the first twelve months of rhGH therapy. BMI z-score >= 0 noted at the beginning of each year of the treatment are associated with significantly better growth increments throughout the first and the second years of the therapy.ConclusionPrepubertal idiopathic GHD children with BMI z-score below 0 would probably benefit from the improvement of their nutritional status prior to the rhGH treatment beginning. It seems that increasing BMI z-score to obtain values between 0 and 1 would be optimal for the growth process.