Objective: Adults with GH deficiency (GHD) exhibit changes in body composition. Studies of the effects of GH substitution on body composition have been short-term or not adequately controlled. The purpose of this study was to evaluate the long-term effects of GH on soft tissue using dual-energy X-ray absorptiometry (DEXA). This technique enables assessment of whole body as well as regional soft tissue composition.
Design: A double-blind, randomized, placebo-controlled study in patients with acquired GHD. The therapeutic regime consisted of biosynthetic human GH (2.0 IU/m2 per day) or placebo, given as a daily subcutaneous injection at 2000 h for 12 months.
Patients: Twenty-nine patients with acquired GHD (GH < 10 micrograms/l (< 20 mU/l) following standard provocative tests) in whom additional hormone replacement was maintained.
Measurements: Soft tissue determinations by DEXA scan, height, weight, foot volume and finger circumference were recorded together with serum IGF-I at baseline and after 12 months.
Results: Twelve months of GH therapy induced a total fat mass (FM) reduction of (mean +/- SEM) 4.88 +/- 0.58 kg (P < 0.002) (n = 13) corresponding to 21.5% of the total FM. The reduction in fat was most marked in the trunk, i.e. 3.07 +/- 0.29 kg (P < 0.002) corresponding to 61% of the total FM reduction. Total lean soft tissue mass (LSTM) increased by 3.31 +/- 0.81 kg (P < 0.001). Regional changes for arm and leg in the GH group amounted to 0.32 +/- 0.08 kg (P < 0.002) and 0.71 +/- 0.14 kg (P < 0.002), respectively, without accompanying significant changes in truncal LSTM between the groups. The foot volume was increased by 55.8 +/- 15.7 ml (P < 0.007) and the finger circumference by 2.67 +/- 0.5 mm (P < 0.005) on active treatment with no significant changes in the placebo group.
Conclusions: Twelve months of GH therapy induced marked changes in soft tissue; fat mass was reduced, particularly in the trunk (61% of total fat mass reduction) whereas lean soft tissue mass increased more in the extremities. The data imply that GH-induced changes in body composition are maintained with long-term therapy.