Tissues of the Laron dwarf are sensitive to insulin-like growth factor I but not to growth hormone.
Tissues from patients with Laron dwarfism are resistant to the actions of endogenous or exogenous GH. As a result, insulin-like growth factor I (IGF-I) levels are low, possibly contributing to the severe growth deficiency that occurs in patients with this syndrome. In this study, we found that erythroid progenitor cells and permanently transformed T-cell lines from two patients with Laron dwarfism responded in vitro to added IGF-I in concentrations ranging between 1-10 ng/mL despite no stimulatory response to added GH in concentrations of up to 500 ng/mL. Normal or near-normal responsiveness to insulin was also demonstrated. The persistence of GH resistance in the cultured T-cell lines confirms the primary genetic nature of the defect in Laron dwarfism. The preservation of in vitro growth responsiveness to IGF-I in hematopoietic tissue from the Laron dwarfs suggests that affected individuals are sensitive to this factor and may respond to it in vivo.
D000293:Adolescent; D000328:Adult; D002455:Cell Division / Q000187:drug effects; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D017977:Deltaretrovirus; D004392:Dwarfism / Q000235:genetics* / Q000473:pathology; D004912:Erythrocytes / Q000473:pathology*; D013006:Growth Hormone / Q000494:pharmacology*; D006412:Hematopoietic Stem Cells / Q000473:pathology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008297:Male; D013002:Somatomedins / Q000494:pharmacology*; D013601:T-Lymphocytes / Q000473:pathology*
D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone