Objective Little is known of the long-term effects of GH replacement therapy on muscle strength in elderly adults with adult onset GH deficiency (GHD). In this study, the effects of 5 years of GH replacement therapy on muscle function were determined in adults over 60 years of age with adult onset GHD.
Design A prospective, open-label, single-centre study.
Patients Twenty-six (12 male and 14 female) consecutive hypopituitary adults with adult onset GHD, mean age 65·0 (range 61–74) years.
Measurements Upper leg muscle strength was measured using a Kin-Com dynamometer. Right and left handgrip strength were measured using an electronic grip force instrument.
Results The mean insulin-like growth factor-I (IGF-I) SD score increased from −1·10 at baseline to 1·21 at end of the study. Body weight was unchanged during the 5-year study. A sustained increase in lean body mass and a sustained reduction of body fat was observed as measured using dual-energy X-ray absorptiometry (DEXA). The GH replacement therapy induced a sustained increase in isometric (60°) knee flexor strength. After statistical correction for age and sex variables using observed/predicted value ratios, a sustained increase was also observed in concentric knee flexor strength at an angular velocity of 60°/s, concentric knee extensor strength at 60°/s and 180°/s, and peak right handgrip strength. At baseline, knee flexor strength was 90–96% of predicted, knee extensor strength was 85–87% of predicted, and hand-grip strength was 74–80% of predicted values. At study end, knee flexor strength was 98–106% of predicted, knee extensor strength was 90–100% of predicted, and hand-grip strength was 80–87% of predicted values.
Conclusion Elderly patients with adult onset GH deficiency had decreased baseline muscle strength also after correction for age and sex. The 5-year GH replacement therapy normalized knee flexor strength and improved, but did not fully normalize, knee extensor strength and handgrip strength.