Potential for growth factor treatment of muscle disease

The recent development of recombinant human growth hormone (GH) and insulin-like growth factor 1 (IGF-1) has provided the opportunity to study the effects of these growth factors in humans. The majority of studies have been performed in healthy young and older adults. Both GH and IGF-1 have shown very positive effects on muscle protein anabolism. Relatively few side effects have developed. Initial studies have shown a beneficial effect of GH in reversing the catabolic actions of oral prednisone, and GH treatment has led to an increase in muscle mass and protein synthesis in pilot studies of myotonic dystrophy. Combination therapy in normal subjects using both GH and IGF-1 has shown encouraging results. There is a greater enhancement of protein anabolism during combined treatment than there is with either agent alone, and concomitant therapy with GH diminished the side effects of IGF-1. It is now feasible to consider therapeutic trials in patients. Future studies of GH and IGF-1 treatment in patients with primary muscle disease and in patients receiving long-term corticosteroid therapy are needed.