Growth hormone and changes in energy balance in growth hormone deficient adults

Background  Adults with growth hormone deficiency (AGHD) have an adverse body composition with an increased prevalence of obesity. It is not known whether growth hormone replacement (GHR) results in alterations in energy intake (EI) and/or energy expenditure (EE). The aim of the study was to investigate the effects of GHR on EI and EE.
Materials and methods  Nineteen hypopituitary adults (14 males, 5 females, mean age 46·2 years) with severe GHD (peak GH response to glucagon ≤ 9 mU L⁻¹) were studied. All patients self-injected recombinant human GH starting with 0·3 mg s.c. daily. The following were measured before and following 6 months of stable maintenance of GHR: food intake during a test meal, appetite ratings, resting EE (indirect calorimetry) and voluntary physical activity (accelerometry).
Results  GHR nearly doubled voluntary physical activity (mean activity units 3319 vs. 1881, P  = 0·007) and improved quality of life score (mean score 9·1 vs. 16·5, P  < 0·0001). Subjects reported higher fasting hunger ratings (mean 64·8 vs. 49·6, P  = 0·02) but ad libitum energy intake remained unchanged. Eating behavioural traits were favourably altered with lower disinhibition (mean 6·0 vs. 7·2, P  = 0·02) and lower susceptibility to hunger ratings (4·6 vs. 6·8, P  = 0·001) after GHR. Additionally, GHR did not result in significant changes in resting EE, body weight and body mass index.
Conclusions  GHR in AGHD significantly improves voluntary physical activity and quality of life. Following GHR, subjects experience greater 'state' (physiological) hunger, reductions in eating disinhibition and hunger susceptibility, but no effects on calorie intake or macronutrient choice were detected.