GH and epidermal growth factor signaling in normal and Laron syndrome fibroblasts.

We have investigated and compared GH and epidermal growth factor (EGF) signaling in primary human skin fibroblasts from normal subjects and subjects with GH-binding protein-positive Laron syndrome (LS). In normal human fibroblasts, GH and EGF activate the tyrosine phosphorylation of signal transducer and activator of transcription (STAT)1 and STAT5b; in LS fibroblasts, EGF does, but GH does not. GH also activates the tyrosine phosphorylation of Janus kinase (JAK)2 in normal, but not LS, fibroblasts.