Response of growth hormone (GH), FFA, blood sugar and insulin to exercise in obese patients and normal subjects

Abstract

Ergometer tests with a constant workload of 600 Kg./min. during 30 minutes were done on eight normal subjects, eight severely obese patients, and two women who had formerly been obese. Arterial blood was sampled three times before, four times during and three times after exercise. The incidence and the height of the GH response were the same in the obese as in the normals. The results show that the obese are able to raise their plasma GH to very high levels if subjected to strenuous exercise. It could not be concluded, however, that they can do so to the same extent as normals, because the exercise was more exhausting for the obese, three of whom had to stop prematurely, than for the normal subjects. In eight of the 12 responders, the rise of GH began almost immediately at the start of bicycling. In all of them, GH valves decreased as soon as work was stopped, irrespective of the time it had lasted. There was no correlation between changes in GH and those on the other parameters measured. It is very probable that the elevation of GH was at least in two thirds of the cases triggered by stress rather than by the increase in energy expenditure. FFA levels were throughout the whole test higher in the obese, than in the normal subjects. No correlation with the GH levels could be found. Blood sugar remained stable in the normal subjects and in the majority of the obese. In three obese patients there was a rise of blood sugar during exercise followed by an elevation of plasma insulin. Two of these patients must be viewed as prediabetics on account of their family history.