The Reds were trailing to Ezequiel Lavezzi's 28th-minute goal in a first half devoid of any real quality on their part.
However, the arrival of Gerrard after the interval completely turned things around and after a couple of near-misses the England midfielder clicked into gear.
He latched onto a gift from former Liverpool defender Andrea Dossena, whose interception diverted the ball towards goalkeeper Morgan de Sanctis but not with enough pace to prevent the 30-year-old reaching it first.
Gerrard then converted a penalty two minutes from time after Glen Johnson was fouled by Salvatore Aronica and he completed his treble with a delicate dink over De Sanctis.
'It was outstanding,' said Hodgson of Gerrard's performance.
'In the first half we hadn't played that badly and were unlucky to be a goal down to an error which was punished.
'His entry onto the field was a catalyst, it galvanised the crowd and the team and the way he scored the first goal epitomised the energy and the spirit the team showed in the second half.
'We owe a big debt of gratitude to him but he will be the first to join me in saying the whole team in the second half gave a good performance.