Glasgow locks Greg Peterson and Scott Cummings will be out for up to six months after both had shoulder surgery.
Scotland Under-20 cap Cummings, 19, was injured in pre-season and United States second row Peterson came off in the recent defeat by Ulster.
Namibian Tjiuee Uanivi is also undergoing investigation on a shoulder injury, while a fourth lock, Tim Swinson (ribs), is also sidelined.
It leaves co-captain Jonny Gray as Glasgow's only fit frontline lock.
With Gray rested for Saturday's Pro12 trip to face Zebre in Italy, Rob Harley - a specialist blind-side flanker - and Robert McAlpine, making his first start after a debut off the bench against Dragons last week, form the second-row partnership in Parma, with Scottish Academy lock Callum Hunter-Hill primed for a possible debut off the bench.
Scotland centres Mark Bennett (head) and Alex Dunbar (back/knee), plus scrum-half Henry Pyrgos (neck), have joined a Warriors injury list currently totalling 13 players.