GH1 and acromegaly: The exosomes with the miRNA were internalized by osteoblasts in vitro, leading to the induction of proliferation and differentiation by interfering with tumor suppressor PDCD4. These miR-21-5p containing exosomes from GH-secreting PitNET also increased bone formation in vivo and therefore may pose an alternative mechanism to the GH-induced growth increase that is linked to acromegaly [84].