IPLEX was to be used in children with short stature whose bodies have problems handling growth hormone because: • they have primary insensitivity to the hormone, so that injected growth hormone has no effect. ‘ Primary’ means that there is no known reason for the insensitivity. • they are not able to make growth hormone and have received growth hormone in the past, but have developed neutralising antibodies, special proteins than can prevent injected growth hormone from having an effect.