- Congenic mice with low serum IGF-I have increased body fat, reduced bone mineral density, and an altered osteoblast differentiation program. Rosen, C.J., Ackert-Bicknell, C.L., Adamo, M.L., Shultz, K.L., Rubin, J., Donahue, L.R., Horton, L.G., Delahunty, K.M., Beamer, W.G., Sipos, J., Clemmons, D., Nelson, T., Bouxsein, M.L., Horowitz, M. Bone (2004)