Low dosages of exogenous growth hormone and its effect on growth in an animal model of suboptimal nutrition

In a previous study, weight gain, insulin growth factor-1 (IGF-1) and insulin growth factor binding protein-3 (IGFBP-3) were increased in rats fed suboptimal levels of energy and administered 0.1 mg/100 g of body weight of recombinant human growth hormone (rhGH). Our objective was to determine whether these anabolic effects were still obtained with lower dosages of rhGH in similarly fed rats. Three groups of male, prepubertal Sprague-Dawley rats were administered rhGH and three groups of similar rats were given normal saline solution daily (0.05 mg/100 g of body weight subcutaneously). All rats were fed a balanced 1:1 carbohydrate:fat ratio diet for 4 wk. Restricted rats within each treatment were pair fed 80% and 60% ad libitum. Daily body weight, food intake, and efficiency were recorded. After 4 wk, serum IGF-1 and IGFBP-3, body fat, fat-free mass, and total body water were determined. Total weight gain and serum IGFBP-3 were significantly higher, with a tendency for increased body fat, in rats treated with rhGH and fed at 60% ad libitum. However, within each treatment, energy restriction caused decreased body fat and total body water. These results suggest that lower dosages of rhGH provide anabolic effects during suboptimal energy intake.