Granulin is a protein that in humans is encoded by the GRN gene. The precursor protein, progranulin, is also called PC cell-derived growth factor. Cleavage of the signal peptide produces mature granulin which can be further cleaved into a variety of active, 6 kDa peptides. Both the peptides and intact granulin protein regulate cell growth. However, different members of the granulin protein family may act as inhibitors, stimulators, or have dual actions on cell growth. Granulin family members are important in normal development, wound healing, and tumorigenesis. Granulins have possible cytokine-like activity. They may play a role in inflammation, wound repair, and tissue remodeling. The human liver fluke contributes to the development of bile duct (liver) cancer by secreting a granulin-like growth hormone. Mutations in the GRN gene have been implicated in up to 25% of frontotemporal lobar degeneration, inherited in an autosomal dominant fashion with high penetrance.