CONTRIBUTION OF GROWTH HORMONE PULSE AMPLITUDE AND PERIODICITY TO MID CHILDHOOD GROWTH - AN ASSESSMENT BY THE SEQUENCE ANALYSIS

Abstract

Mid childhood growth has been studied in 21 short children (14M, 7F) aged 5.2-11.9 years growing with height velocity (HV) SDS between O and -0.8 (Group A) and 29 short children (21M,7F) growing with HV SDS < -0.8 (Group B). 24 hr GH profiles were analysed by an iterative method of pulse detection and subjected to time sequence analysis to determine dominant periodicities within the data array. Children aged <7 years from Group A had a dominant periodicity of 5 hours but after this age there was a shift to a 3 hour periodicity. In the whole sample (Groups A and B), differences between growth rate could be explained entirely by pulse amplitude. The modulation of childhood growth by GH pulse amplitude persisted into puberty in 14 tall pubertal girls in whom the periodicity of GH secretion remained unchanged. 6 children from Croup B had a similar sum of GH pulse amplitudes to the Group A children but a faster pulse frequency (11-14 pulses/24 hours) with a dominant periodicity of 2.3 hours. This led to a HV SDS -1.1- -3.0. We define this codition as neurosecretory dysfunction. To grow at a normal velocity a child needs 6 - 9 GH pulses/24 hours. We conclude that mid childhood and pubertal growth is GH pulse amplitude modulated with a periodicity of 3 hours. The major cause of poor growth velocity is low GH pulse amplitude but a sub group exists in which disturbance of pulse frequency is the major contributor.