Influence of the insulin-to-growth hormone ratio on body composition of mice

To determine whether the insulin-to-growth hormone ratio was different in genetically related animals with known differences in food intake and amount of adipose tissue the following parameters were measured in lean (C57BL/6J) and yellow obese mice (Avy/a): food intake, body composition, energy intake, plasma concentrations, and ratios of insulin and growth hormone; these were determined in one experiment during a 24-h period. Yellow obese mice contained significantly greater amounts of body fat than the lean littermates, a significantly higher insulin-to-growth hormone ratio, and a higher daily food intake. In a second experiment, a shift in hormone concentrations and ratios occurred with increasing age and simultaneously with changes in body composition in the Avy/a mice; both changed without changes of food intake. The increased obesity may have resulted from an increase in the insulin-to-growth hormone ratio or more probably from an increase in the insulin level alone.