Under NRL rules, all 16 teams must have 30 players on their books by August 1, although players let go after the start of the season don't need to be replaced.
Turuva and Jenkins were already part of the development squad for this season and have been upgraded to the top 30 for the remainder of the season.
Turuva, who starred for Fiji in the recent Pacific Test, is locked into the club until the end of the 2024 season and could be included for the end of year Rugby League World Cup in England.
Jenkins, on the other hand, is rated as a future NRL star, but is only locked in at the foot of the mountains until the end of the 2023 season.
Henry's contract meanwhile sees him join the development squad early - he was due to join in 2023, before being promoted into the NRL Top 30 squad from 2024.
“On behalf of all at Panthers, I’d like to congratulate Sunia, Thomas and Liam on signing contract upgrades with the club,” Panthers Rugby League CEO Matt Cameron said in a club statement.
“Having all progressed through the Panthers pathways system, the contract upgrades are great examples of the built from within culture we have cultivated at Panthers.
"With Liam having played his junior football at Blayney Bears and Thomas at Young Cherrypickers, their commitment to Panthers highlights the club’s strong relationship with the western corridor and country rugby league.
“Not only has the trio developed into quality rugby league players, but they are also quality men off the field.”
All three players are Penrith pathways players, continuing the rich talent base the club have built out of their academy.