Shares of UnitedHealth Group Inc. shot up more than 9 percent in premarket trading Thursday after the insurer released earnings that met expectations and offered some reassurance to Wall Street.

Minnetonka, Minn.-based UnitedHealth reported a 28 percent drop in third-quarter profit, driven in part by higher operating costs, lower investment income and settlements for class-action lawsuits. The second-largest U.S. health insurer said its net earnings fell to $920 million, or 75 cents per share, in the quarter ending Sept. 30, down from $1.28 billion, or 95 cents per share, in the same quarter last year.

But UnitedHealth also said revenue rose 8 percent to $20.2 billion from $18.7 billion a year ago.

Its adjusted profit was 73 cents per share, excluding a 2-cent benefit from a change in the estimate of net costs to settle a couple stock option-related lawsuits.