Yakar, S, Rosen, C J, Beamer, W G, Ackert-Bicknell, C L, Wu, Y, Liu, J L, Ooi, G T, Setser, J, Frystyk, J, Boisclair, Y R & LeRoith, D 2002, ' Circulating levels of IGF-1 directly regulate bone growth and density ', J. Clin. Invest., vol. 110, no. 6, pp. 771-781 .