Progranulin is a growth factor involved in the regulation of multiple processes 
including tumorigenesis, wound repair, development, and inflammation. The recent 
discovery that mutations in the gene encoding for progranulin (GRN) cause 
frontotemporal lobar degeneration (FTLD), and other neurodegenerative diseases 
leading to dementia, has brought renewed interest in progranulin and its 
functions in the central nervous system. GRN null mutations cause protein 
haploinsufficiency, leading to a significant decrease in progranulin levels that 
can be detected in plasma, serum and cerebrospinal fluid (CSF) of mutation 
carriers. The dosage of circulating progranulin sped up the identification of 
GRN mutations thus favoring genotype-phenotype correlation studies. Researchers 
demonstrated that, in GRN null mutation carriers, the shortage of progranulin 
invariably precedes clinical symptoms and thus mutation carriers are "captured" 
regardless of their disease status. GRN is a particularly appealing gene for 
drug targeting, in the way that boosting its expression may be beneficial for 
mutation carriers, preventing or delaying the onset of GRN-related 
neurodegenerative diseases. Physiological regulation of progranulin expression 
level is only partially known. Progranulin expression reflects mutation status 
and, intriguingly, its levels can be modulated by some additional factor (i.e. 
genetic background; drugs). Thus, factors increasing the production and 
secretion of progranulin from the normal gene are promising potential 
therapeutic avenues. In conclusion, peripheral progranulin is a nonintrusive 
highly accurate biomarker for early identification of mutation carriers and for 
monitoring future treatments that might boost the level of this protein.