Low dose orally administered arginine is able to enhance both basal and growth hormone-releasing hormone-induced growth hormone secretion in normal short children

Aim of this study was to verify whether arginine (ARG), which likely inhibits hypothalamic somatostatin release, has an enhancing effect on the GHRH-induced GH rise, even when administered orally at low dose. To this goal we studied the effects of 4 g orally administered ARG, either hydrochloride (ARG-H) or aspartate (ARG-A), on both basal and GHRH (1 μg/Kg iv) -stimulated GH secretion in 31 children with familial short stature (11 males and 20 females, aged 5.5–13.8 yr, pubertal stage l–lll, and compared the results with those of iv infusion of 0.5 g/kg ARG-H. Oral ARG-H (Group A,n=11) induced a significant increase of basal GH levels (4.2±1.3 vs 1.0±0.4 μg/L, p<0.02) and enhanced the GH response to GHRH (41.1±8.6 vs 25.3±6.7 μg/L, p<0.02). Oral ARG-A (Group B, n=10) induced a slight, but not statistically significant increase in serum GH levels (3.4±1.5 vs 1.0±0.3 μg/L) and enhanced the GHRH-induced GH rise (49.7±9.8 vs 26.1±8.4 μg/L, p<0.05).Intravenous ARG-H (Group C, n=10) stimulated basal GH levels (6.2±1.2 vs 1.2±0.3 μg/L, p<0.005) and increased the GHRH-induced GH rise (46.7±5.0 vs 17.1 ± 2.3 μg/L, p<0.005). This response was similar to those after oral ARG-H or ARG-A plus GHRH. No variation was observed in PRL levels after oral ARG (either ARG-H or ARG-A) and/or GHRH. These results show that a low dose of orally administered ARG is able to enhance the GHRH-induced GH rise with the same extent of a high dose iv administered ARG in normal short children. The potential usefulness of oral ARG combined with GHRH to restore GH secretion in hypothalamic GH deficiency might be envisaged.