The insulinogenic function of the pancreatic islets was assessed by the use of tolbutamide stimulation in 25 children with hyposomatotrophic dwarfism (HSD). The authors suggest that the low insulin release and/or synthesis is responsible for slight growth response of these children to HGH treatment. There may also be a causative relation between this low insulin response and the tendency of children with HSD to develop diabetes after HGH treatment.