Liver specific transgene overexpression of IGF-I results in increased levels of circulating IGF-I and increased body weight. A.) Overexpression of liver IGF-I (black bar) resulted in a significant (p < 0.01) increase in female serum levels of IGF-I measured at 6 weeks of age compared to mice without the TTR-IGF-I transgene (white bar). B.) Females expressing the IGF-I transgene exhibited significantly (p < 0.05) larger body weights at 7, 10-12 weeks of age due to increased circulating IGF-I compared to wt/ErbB2 only controls. No transgene = wt + ErbB2 only females; IGF-I Transgene = TTR-IGF-I transgenic + TTR-IGF-I-ErbB2 bigenic females. N for each group is represented within their respective bars. N = 30 animals per group for weight. ** p < 0.01; * p < 0.05.