The aim of the present study is to examine the effect of neuropeptide Y and estrogen on type IIb sodiumcoupled phosphate co-transporter (NaPi-IIb) gene expression and activity. Uptake studies with human intestinal cell line, Caco-2 cells, showed that treatment with neuropeptide Y and estrogen concentration-dependently increased sodiumdependent phosphate absorption. Reverse transcriptase-polymerase chain reaction analysis indicated that expression of NaPi-IIb mRNA was also increased after Y treatment with neuropeptide and estrogen. These studies show for the first time that neuropeptide Y increased intestinal sodium-dependent phosphate absorption. This increase is associated with the increase of the expression of NaPi-IIb mRNA