Second, the factor produced by the neoplasm must possess sufficiently potent biological activity to develop humoral syndromes. As shown in Fig. 21.3, detection frequencies and tissue concentrations of peptides such as gastrin-releasing peptide (GRP), calcitonin and growth hormone-releasing hormone (GHRH) have a tendency to be higher than those of ACTH and ADH in tumours although clinical syndromes associated with these peptide hormones were not observed.
