Somatomedin and the regulation of skeletal growth

Somatomedin is a polypeptide(s) which "mediates" the actions of growth hormone. This pituitary dependent hormone was previously called "sulfation factor," a term derived from the bioassay technique which measures the incorporation of radioactive sulfate into cartilage glycosaminoglycans. Somatomedin has a more general effect upon cartilage; it is necessary for the cell multiplication and cartilage maturation which results in the growth of long bones. Somatomedin is not found in the plasma in growth hormone deficiency and appears following growth hormone administration. A genetic defect in somatomedin synthesis has been identified in the Laron's dwarf. Growth hormone is present in excess in the plasma and growth hormone administration does not stimulate somatomedin synthesis in this syndrome. Insufficient data are available to delineate the role for somatomedin in other growth disturbances. It has been demonstrated that glucocorticoid hormones interfere with both somatomedin synthesis and its biological activity. Purification of somatomedins in plasma has been achieved and radioreceptor or radioimmunoassays will be available in the future for study of growth problems in children.