Effects of exogenous recombinant human growth hormone on an animal model of suboptimal nutrition

Background: Nutritional dwarfing, a form of suboptimal nutrition, has been identified as a frequent cause of short stature and delayed sexual development in children. Retarded growth is an adaptive response to suboptimal nutrition. Objective: To assess whether recombinant human growth hormone (rhGH) may promote growth during various levels of suboptimal nutrition. Methods: Using a previously developed rat model of suboptimal nutrition, six groups of rats (six rats/group) were fed a balanced 1:1 carbohydrate:fat ratio diet for 4 weeks. Three of the groups were administered daily injections of rhGH (0.1 mg/100 g BW) subcutaneously in the back while the other three groups were kept as controls and were given similar dosages of normal saline solution (NSS), Restricted rats within each treatment group were pair fed 80 and 60% of the ad-libitum rats intake. Daily intake of the 80 and 60% fed groups were determined based on the intake of the ad-libitum fed groups. Serum IGF-I and insulin were determined after 4 weeks of dietary treatment by radioimmunoassay while IGFBP-3 was determined by an immunoradiometric assay. Body composition was assessed in all rats by carcass analysis. Results: After 4 weeks, total weight gain and tail growth were higher (p<0.05) in the rhGH treated group at 80 and 60% of-libitum energy intake. Serum levels of IGF-I and IGFBP-3 were higher (p<0.05) in rhGH treated rats fed at 60% of ad-libitum. In comparison to the NSS groups, administration of rhGH in rats fed ad-libitum increased total body water. Energy restriction caused decreased fat percentage (p<0.05) in both rhGH and NSS groups without differences among treated groups. Conclusion: These results suggest that the anabolic effects of rhGH may overcome mild to moderate energy restriction.