The phenotype of GH-resistant states (pseudohyposomatotropinaemia) (Fig. 14.22) is identical to the GH-insufficient child. The defect, however, lies in the GH receptor or in the transcription of the GH message. The hallmark of GH insufficiency is a low concentration of insulin-like growth factor I (IGF-I), with a low random GH level; in pseudohyposomatotropinaemia, the IGF-I concentration is low while GH levels are high. These patients do not respond to exogenou GH.
