The effect of growth hormone (GH) replacement on muscle strength in patients with GH-deficiency: a meta-analysis.

Abstract

CONTEXT/OBJECTIVES: GH replacement increases muscle mass and reduces body fat in growth hormone deficiency (GHD) adults. A recent meta-analysis has demonstrated that this improvement in body composition is associated with improved exercise performance. The current meta-analysis was carried out to determine whether high-quality evidence exists to support a beneficial effect of GH replacement on strength. DESIGN/METHODS: An extensive Medline search/literature review identified eight studies with utilizable, robust data, involving 231 patients in nine cohorts. Previously unpublished data were sought from authors and obtained in two cases. All studies included were randomized, double-blind, placebo-controlled, of parallel or cross-over design and of an average 6.7 months duration. Information was retrieved in uniform format, with data pertaining to patient numbers, study-design, GH-dose, mean age, IGF-I levels and muscle strength measurements (isometric or isokinetic quadriceps strength) recorded. Data were analysed using a fixed-effects model, utilizing continuous data measured on different scales. A summary effect measure (d(s)) was derived for individual strength variables, whereas an overall summary effect was derived from the sum of all studies incorporating different variables; 95% CIs were calculated from the weighted variances of individual study effects. RESULTS: Analysis revealed no significant improvement, neither when all studies were combined (d(s) = +0.01 +/- 0.26) nor when measured individually (isometric quadriceps strength, d(s) = +0.02 +/- 0.32 and isokinetic quadriceps strength, d(s) = 0.00 +/- 0.45). CONCLUSIONS: Evidence from short-term controlled studies fails to support a benefit on muscle strength of GH replacement in GHD patients, which is likely to occur over a longer time-course, as seen in open-label studies.