Twenty-four-hour patterns of plasma growth hormone concentrations were evaluated during 50 studies of 42 subjects with juvenile-onset diabetes mellitus. Blood was sampled continuously over 24 h using a portable peristaltic pump under conditions in which subjects remained ambulatory and maintained their daily dietary and insulin regimens. All diabetics showed diurnal patterns characterized by frequent episodes of secretion of growth hormone. The mean 24-h concentration of growth hormone, designated the integrated concentration, was significantly higher among juvenile-onset diabetics (P < 0.001) than it was in ageand sex-matched nondiabetic populations. Juvenileonset diabetics younger than 20 yr had significantly higher (P < 0.005) growth hormone integrated concentrations than did older juvenile-onset diabetics. There was no statistically significant correlation between the integrated concentrations of glucose and growth hormone; thus, the study failed to provide us with support for the hypothesis that elevated growth hormone concentrations in diabetics are a consequence of hyperglycemia. Variability of diurnal glucose concentrations was positively correlated (P < 0.015) with the growth hormone integrated concentration among juvenile-onset diabetics. Our observations indicate that rapid declines in plasma glucose concentration or episodes of absolute hypoglycemia were significant factors, contributing to both the elevated integrated concentration and the secretory spiking of growth hormone observed in the diabetic population,

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