Shares in ResMed plunged more than 13 per cent on Monday after results over the weekend from a weight-loss drug trial resurfaced investor doubts about the sleep apnoea treatment provider’s key market.

The shares – which rank among the most widely held by Australian fund managers – lost $4.22 to $27.74 on Monday morning, following the results from pharmaceutical giant Eli Lilly that its tirzepatide weight-loss treatment reduced obstructive sleep apnoea severity in trial patients.