The puberty-related increases in cNF growth may be due to changes in endocrine signalling;90 cNFs from NF1 patients have increased immunohistochemical staining for growth hormone receptor (GHR), compared with sporadic cNF and the ligand for GHR is increased during normal puberty.90 Growth hormone (GH) hypersecretion has been observed in some NF1 patients, but other studies have concluded that NF1 patients have GH deficiency,91–93 and thus the interplay between GH and cNF growth remains unclear at present. This evidence concerns the gene GHR and neurofibromatosis type 1.