The observation that CGL was required for lowering circulating levels of T4 and IGF-1 in two different models of hypothyroidism, combined with the ability of TH to activate GHR/IGF-1 gene expression (Koenig et al., 1987, Tsukada et al., 1998), suggests that the compromised ability to reduce circulating T4 may be partially responsible. The gene discussed is TH; the disease is hypothyroidism.