J. Endocrinol. Invest. 25: 769-772, 2002 769 ABSTRACT. The aim of this study was to evalu- ate the relationship between GH and leptin in a group of short children and adolescents. Leptin and GH serum levels were measured before and during pharmacological stimulation tests (argi- nine and insulin) in a group of 45 children (30 male, 15 female), mean age 8.6±3.9 yr, affected by idiopathic isolated GH deficiency (GHD), and in a group of 27 children (15 male, 12 female), age 10.9±3.3 yr, with constitutional growth de- lay. Results showed that basal and peak leptin levels as well as the AUC were significantly high- er in GHD patients compared to controls (p<0.05) and correlated with BMI SDS (p<0.0001) in GHD patients. No change in leptin serum levels was observed during either stimulation test. No cor- relation was found, however, between basal lep- tin serum levels and basal, peak and the AUC of GH during the tests. Moreover, no correlation was found between the acute changes of serum GH concentration during both stimulation tests and leptin serum levels. The results suggest that leptin and GH secretion is not correlated and that leptin serum levels mainly reflect the amount of fat tissue, which is higher in GHD pa- tients. (J. Endocrinol. Invest. 25: 769-772, 2002) © 2002, Editrice Kurtis INTRODUCTION It is becoming clear that leptin should no longer be considered as just a hormone modulating appetite control and energy expenditure, but rather as an hy- pothalamic neuromodulator controlling the secre- tion of many pituitary hormones (1). Leptin has been shown to play a major role in sexual development in both animals (2) and humans (3, 4), and to influence spontaneous GH secretion in rats (5) and IGF-I gene expression in the liver, independently of GH (6). It has been suggested that leptin could inhibit GH secretion in humans, the latter being inversely cor- related to body fat (7). Moreover, an inverse rela- tionship between leptin and GH has been demon- strated (8), although there is no direct evidence of the role of leptin in inhibiting GH secretion. Whether GH can influence serum leptin levels is still a mat- ter of debate. Sudden changes of GH following argi- nine infusion do not seem to alter leptin serum lev- els (9), while acute GH treatment led to an increase in leptin levels after 24 h in elderly (10) and young patients affected by GH deficiency (GHD) (11), fol- lowed by a significant decrease after 72 h (12). Chronic GH treatment has been shown to reduce leptin levels in GHD children (13) and to have no ef- fect in elderly GHD patients (10). The aim of our study was thus to verify, in a group of 45 children affected by GHD and in 27 controls, 1) whether a basal leptin value could predict the re- sponse of GH to a pharmacological stimulus (arginine or insulin); 2) the relationship between GH and leptin serum levels during the test; and 3) the effect of argi- nine and insulin infusion on leptin serum values. MATERIAL AND METHODS Subjects Seventy-two children were investigated because of short stature: 45 of them (30 boys, 15 girls) were considered to be GHD, while the remaining 27 (15 boys, 12 girls) were only growth retarded and served as controls. Their auxological da- ta are shown in Table 1. Key-words: Leptin, GH, GH deficiency, arginine infusion, insulin-induced hypoglycaemia. Correspondence: Dr. Giorgio Radetti, Dipartimento di Pediatria, Ospedale Regionale, Via L. Boehler 5, 39100 Bolzano, Italia. E-mail: giorgio.radetti@asbz.it Accepted May 2, 2002. Serum leptin levels are not influenced by arginine and insulin infusion and by acute changes of GH G. Radetti*, C. Tinelli**, C. Paganini*, M. Draghi***, D. Scarcella****, E. Bozzola***, G. Aimaretti*****, G. Rondini***, and L. Tatò**** *Department of Pediatrics, Regional Hospital of Bolzano, Bolzano; **Biometric Unit-IRCCS San Matteo, Pavia; ***Department of Pediatrics, University of Pavia, Pavia; ****Department of Pediatrics, University of Verona, Verona; *****Division of Endocrinology and Metabolism, University of Turin, Turin, Italy