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The Effect of Growth Hormone Replacement on Exercise Capacity in Patients with GH Deficiency: A Metaanalysis

Department of Endocrinology and Diabetes, Adelaide and Meath Hospital, Tallaght, Dublin 24, Ireland

Address all correspondence and requests for reprints to: James Gibney, Department of Endocrinology and Diabetes, Adelaide and Meath Hospital, Tallaght, Dublin 24, Ireland. E-mail: james.gibney{at}amnch.ie.

Context/Objectives: GH replacement in GH-deficient adults exerts clear effects on body composition, but there is a lack of high-quality evidence concerning its functional effects, which are more clinically important. This metaanalysis was carried out to determine the effects of GH replacement on exercise performance.

Design/Methods: A Medline search and examination of reference lists of included studies and relevant review articles identified 11 studies with utilizable, robust data, involving a total of 268 patients. All included studies were randomized, double blind, placebo controlled, and of either parallel or crossover design. Information was retrieved in uniform format, with data pertaining to patient numbers, study design, GH dose, age, IGF-I levels, and the exercise variables maximal oxygen uptake and maximal power output recorded. The data were analyzed using a fixed-effects model, using continuous data measured on different scales. A summary effect measure (d_s) was derived for the individual exercise parameters, whereas an overall summary effect was derived from the sum of all studies across different variables; 95% confidence intervals were calculated from the weighted variances of individual study effects.

Results: GH replacement was associated with significant improvement with all studies combined (d_s = +0.32, 0.08–0.56), for maximal power output (d_s = +0.4, 0.06–0.74), and maximal oxygen uptake (d_s = +0.34, 0.07–0.62). There was no association between age or GH dose on the degree of improvement.

Conclusions: There is strong evidence that GH replacement improves exercise performance in GH-deficient patients. This evidence should be considered when decisions are made regarding prescription of GH.