 The aim of the present protocol is to evaluate the effects of GH treatment in long-term steroid treated children, on muscle mass, and muscle strength. It will be an open, randomized, controlled, 2-parallel group study. The follow-up in this study will be one year. The objective of this study will be to evaluate short-term effects of GH treatment on muscle mass, muscle strength and body composition in children suffering from various diseases requiring steroid therapy. Expected pathologies are juvenile idiopathic arthritis, nephrotic syndrome, uveitis, systemic diseases and organ transplantation. Changes in muscle mass will be assessed by measuring the muscle and sub-cutaneous fat on the cross sectional area of the thigh by MRI. MRI offer the advantage of non-invasive technique, allowing serial and accurate measurements.Muscle strength will be performed by serial muscular testing of different muscular groups. Body composition will be assessed by DEXA. DEXA allows rapid, accurate and highly reproductible determination not only of bone mass but also of lean and fat mass of the whole body, with very low radiation exposure.It appears to be the most sensitive method for assessment of muscle wasting as well as of fat repartition that contribute to Cushings appearance in steroid treated patients. 