EFFECTS OF ORAL GLUCOSE-ADMINISTRATION ON SPONTANEOUS AND GROWTH-HORMONE (GH)-RELEASING HORMONE-STIMULATED GH RELEASE IN CHILDREN AND ADULTS

It has been suggested that hypothalamic regulation of GH secretion in children may differ from that in adults. On the other hand, there is e vidence that oral glucose administration affects GH secretion through hypothalamic mechanisms. Therefore, we investigated spontaneous and GH RH-stimulated (1 mu g/kg BW) GH responses after oral glucose administr ation (children, 1.75 g/kg BW; adults, 75 g) in peripubertal normal ch ildren (13 girls and 13 boys, aged 11.7 +/- 0.4 yr; range, 8-13) and h ealthy adults (12 males and 14 females, aged 25.7 +/- 1.2 yr; range, 1 8-39). Three studies were carried out. In study 1, serum GH levels in 8 children were suppressed (<1 mu g/L) for 135 min after oral glucose administration. Afterward, there was a rise in serum GH levels. In 8 a dults, the suppressive effect of glucose persisted throughout the 210- min study period, and no GH rebound appeared. In study 2, the GH respo nses to iv GHRH boli in 10 adults and 10 children were, respectively, inhibited, unchanged, or augmented by an oral glucose load administere d 30, 60, or 120 min before GHRH challenge. In study 3, oral glucose a dministration to 8 adults greatly enhanced the GH response to GHRH giv en 180 min after the glucose, whereas in 8 children, the GH response t o GHRH was unchanged. In conclusion, glucose affects basal and GHRH-st imulated GH release in a similar manner in adults and children, indica ting that neuroregulatory influences of glucose on the GH axis may not differ in the two age groups. In children, however, the duration of b oth the initial inhibitory and subsequent stimulatory effects of gluco se administration on GH secretion is shorter.