IGF1 and amyotrophic lateral sclerosis: This important anabolic hormone has direct and indirect actions on protein synthesis of different tissues, including skeletal muscle.40, 41 Importantly, the indirect effects of GH are mediated mainly through the production of IGF-1.42, 43 Morselli et al. found that the majority (73%) of ALS patients have a GH deficiency, and thus this condition could induce a reduction of tissue IGF-1 synthesis.44