Effects of exogenous growth hormone on growth and body composition in genetically selected mice.

The effects of exogenous GH on growth and body composition were investigated in lines of mice selected for high or low body weight (P-lines) or high or low body fat (F-lines). Mice from all lines were given daily injections of recombinant bovine GH or a placebo for 21 days from 4 weeks old. They were killed and various organ weights measured. There was no consistent effect of GH on organ weights. In all lines of mice the rate of weight gain and final weight increased in response to GH. In both lines selected for body fat, GH treatment decreased fat content. The low body weight mice also became less fat, but in the high body weight mice GH treatment increased fat percentage. The results indicate that the differences in growth rate and body composition observed in these lines are not due to differences in responsiveness to GH.