Body size and bone length are increased in GHR–/– mice after IGF-I treatment. (a) Representative photograph of 6-week-old wild-type (left), GHR–/– (center), and GHR–/– treated with IGF-I (6 mg/kg/d) from age 2 to 6 weeks (right). (b) Body weight in untreated (open circles) and IGF-I–treated knockout mice. Mice were treated with IGF-I from weeks 2–6 (dark gray square), 4–6 (light gray triangle), or 2–4 (gray diamond). (c) Body length at 6 weeks of age was increased by all IGF-I treatment regimens. (d) Femoral length was significantly increased only in mice treated for 4 weeks. n = 5–10 per group. AP < 0.001 vs. wild-type, BP < 0.001, CP < 0.01, DP < 0.05 vs. GHR–/–.