Dan Potts has joined Sky Bet League Two side Portsmouth on loan until 21 December.
The 19-year-old defender will get a second taste of the Football League, having enjoyed a loan spell with Colchester United last season.
Potts has been a mainstay of Nick Haycock's Development Squad, who have stormed to the top of the Barclays U21 Premier League with a fine start to the season, scoring twice in six league appearances.
He also started at left wing-back in the Hammers' 2-0 victory over Burnley in the Capital One Cup fourth round late last month.
That first team run-out added to the ten he has already made at that level in his fledgling career, and he will now bolster his experience with a month at Fratton Park.
Guy Whittingham's men currently sit 16th in League Two, but are only six points off the Play-Offs in a tight division and Potts could make his debut in a home match against Scunthorpe United this Saturday.
The Hammers youngster joins Elliot Lee (Colchester United), Jordan Spence (MK Dons) and Paul McCallum (Torquay United) out on loan at Football League clubs.