Insulin-like growth factor I (IGF-1) is an important peptide synthesized in response to growth hormone stimulation. Alternative promoters and an elaborate alternative splicing regulated in a tissue- and developmentally-specific manner result in the production of several distinct isoforms of IGF-1 [reviewed in Gorecki et al. (2007); Matheny et al. (2010)]. The predominant form, IGF-1Ea is a circulating factor produced in the liver while IGF-1Eb and IGF-1Ec (Mechano-Growth Factor, MGF) are expressed in specific tissues in response to different, often pathological stimuli and appear to have some specific functions in these different tissues [reviewed in Aberg et al. (2006); Gorecki et al. (2007); Matheny et al. (2010)].