There are evidences of functional growth hormone (GH) deficiency, expressed by means of low serum levels of insulin-like growth factor 1 (IGF-1), in a subset of fibromyalgia patients. The efficacy of low GH doses versus placebo has been demonstrated in this population. We assessed the efficacy and safety of GH added to standard therapy compared to standard therapy alone in the treatment of severe, prolonged and well-treated fibromialgya patients with low IGF-1 levels.