GROWTH HORMONE SECRETION IN CHILDREN DETERMINED BY TIME SERIES ANALYSIS

Mid childhood growth has been studied in 26 short children (18M;8F) aged between 5.2 and 11.9 years growing with height velocity standard deviation score (SDS) between 0 and -0.8 and 24 short children (17M;7F) growing with height velocity SDS less than 0.8. Twenty-four hour GH profiles were analysed by an iterative method of pulse detection and subjected to time series analysis to determine dominant periodicity within the data arrays. Children aged less than 7 years displayed no dominant periodicity but after this age a periodicity of 200 min emerged. In the whole sample, differences between growth rate could be explained entirely by pulse amplitude. Nevertheless, the normal decline in height velocity over this age period occurred despite a significant shift in periodicity and an increase in GH pulse amplitude. This modulation of childhood growth by GH pulse amplitude persisted into puberty and the pubertal growth spurt of 14 tall girls was shown to be amplitude modulated with the periodicity unchanged. We conclude that mid childhood and pubertal growth is GH pulse amplitude modulated with a periodicity of approximately 200 min.