Effects of four years' treatment with biosynthetic human growth hormone (GH) on body composition in GH-deficient hypopituitary adults

Abstract

Short-term trials of growth hormone (GH) substitution in hypopituitary adults have shown beneficial effects on body composition. To evaluate the long-term effects on body composition, we followed thirteen GH-deficient adults (GH < 6 mU/l following standard provocative tests) for 4 years of GH replacement. At yearly intervals, serum insulin-like growth factor I (IGF-I), body weight, body mass index (BMI), waist, waist-to-hip circumference ratio (WHR) and resting systolic (SBP) and diastolic blood pressure (DBP) were determined, and body composition was assessed using three independent methods: total body potassium (TBK), bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA). Compared to baseline, IGF-I levels increased significantly at 1 (p = 0.0001), 2 (p = 0.0004), 3 (p = 0.006) and 4 years (p = 0.002). Body weight and BMI changed minimally at 1, 2 and 3 years and increased significantly only at the fourth year (p = 0.012 and p = 0.0009, respectively) of GH therapy. Waist and WHR decreased significantly at 1, 2 and 4 years (waist: p = 0.0009, p = 0.0004, p = 0.049; WHR: p = 0.0025, p = 0.012, p = 0.047, respectively). Neither resting SBP nor DBP changed significantly. Fat-free mass (FFM) derived from TBK and BIA increased significantly at 1 (p = 0.004; p = 0.004), 2 (p = 0.003; p = 0.05), 3 (p = 0.005; p = 0.04) and 4 years (p = 0.02; p = 0.002). Using DXA, the increase in FFM was significant at 1 (p = 0.007) and 2 years (p = 0.008) but not at 3 and 4 years. Percentage body fat measured by TBK, BIA and DXA decreased significantly at 1 (p = 0.008; p = 0.003; p = 0.03), 2 (p = 0.018; p = 0.06; p = 0.049) and 4 years (p = 0.03; p = 0.002; p = 0.04). A rise in total body water, calculated from BIA, was observed at 1 year (p = 0.004) and was maintained throughout the treatment period. These data demonstrate that 4 years of GH treatment in hypopituitary adults is associated with sustained improvement in body composition.