The Somatomedin and Dual Effector Theories of Growth Hormone Action
Submitted by Alan D. Rogol, M.D., Ph.D.
The somatomedin hypothesis stated that the uptake of sulfate in, for example rat costochondral, cartilage was due to a GH-dependent factor rather than GH itself. The key experiment noted that GH or serum from an hypophysectomized rat added to the incubation medium produced little or no uptake of sulfate; however, serum from an hypophysectomized rat pre-treated with GH led to a several-fold increase in sulfate uptake (Salmon and Daughaday J Lab Clin Med 1957; 49:825). This hypothesis was updated by Green, and co-workers to define the individual activities for GH and IGF-1 (somatomedin) in which GH promotes the differentiation of precursor cells, e.g., within the growth plate, and locally produced IGF-1 leads to clonal expansion (Differentiation 1985; 29(3):195).