The effect of synthetic very low calorie diets on the GH-IGF-1 axis in obese subjects.
IGF-1 concentrations were measured in plasma from 20 obese patients and 20 age- and sex-matched control subjects all of whom were fasting. Plasma IGF-1 concentrations were lower (p less than 0.05) in the obese individuals than in the controls. Plasma GH and insulin responses to stimulation with oral glucose were measured in 7 healthy normal weight individuals and both before and after energy restriction in 7 obese individuals. Before treatment the obese individuals were hyperinsulinaemic (fasting and integrated stimulated concentrations p less than 0.05) and showed attenuation of the plasma GH response to stimulation (peak and integrated stimulated values p less than 0.05 and less than 0.005, respectively) following oral glucose when compared to normal weight controls. Plasma insulin levels fell (both fasting and integrated concentrations p less than 0.05 and less than 0.005, respectively) and stimulated plasma GH responses increased (both peak and integrated values p less than 0.01 and less than 0.05, respectively) in the obese individuals following 3 wk treatment with a synthetic very low energy diet. Plasma IGF-1 concentrations remained unchanged during energy restriction. These results fail to support an endocrine IGF-1 mediated feedback inhibition on the hypothalamic-pituitary axis as the cause of the attenuated release of GH in obesity.
Department of Clinical Biochemistry and Clinical Nutrition, St. Luke's Hospital, Guildford, Surrey, UK.
R
R
Gama
J D
JD
Teale
V
V
Marks
D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D004038:Diet, Reducing; D005246:Feedback; D005260:Female; D005526:Food, Formulated; D013006:Growth Hormone / Q000097:blood*; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D009765:Obesity / Q000097:blood* / Q000178:diet therapy; D010913:Pituitary-Adrenal System / Q000378:metabolism; D013002:Somatomedins / Q000032:analysis*
D001786:Blood Glucose; D007328:Insulin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone