Growth hormone secretion in normal prepubertal children: importance of relations between endogenous secretion, pulsatility and body mass.
OBJECTIVE: Although a negative relation between GH secretion and body mass has been described, few studies have been carried out in prepubertal subjects of normal weight and height. The aim of the present study was to examine the relations between GH secretion, pulsatility and body mass throughout the wide range of weights in normal prepubertal children. METHODS: We determined integrated GH concentrations during the day (IC-GHD), night (IC-GHN), and 24 hours (IC-GH24) in 46 prepubertal children (26 males, 20 females) of normal height and growth velocity and with a Z-score (BMI-SD) between +2 and -2 SD. In addition, in 28 of these patients randomized by their BMI-SD, the secretory profile was studied by the Pulsar program: area under curve (AUC), peak number (NP), high spontaneous peak of secretory profile (HSP), and area of pulses (AP) which were considered large (L) or small (S) if their amplitude was greater or less than 4 micrograms/l (8 mU/l). RESULTS: BMI-SD correlated negatively with IC-GH (IC-GHD, IC-GH24, r = -0.58, P < 0.001) and with Pulsar parameters r = -0.48, P < 0.001; IC-GHN, r = -0.45, P < 0.001; (AUC-24, r = -0.73, P < 0.0001; HSP, r = -0.65, P < 0.0001). The NP correlated negatively with BMI-SD (r = -0.51, P < 0.005) at the expense of NLP (r = -0.54, P < 0.003) without being significantly correlated with NSP. This inverse correlation between BMI-SD and NLP was greater during daytime (NLDP, r = -0.60, P < 0.001) and was not significant at night. NSP did not correlate with BMI-SD. A similar relation was observed with respect to pulse area (ALP, r = -0.38, P < 0.05; ALDP, r = -0.46, P < 0.02;) and was not significant for ALP during the night or for ASP in any period. CONCLUSIONS: We suggest that it should be necessary to relate GH secretion to body mass in prepubertal children before defining their secretion as normal or pathological.