Stephen Hemsley ran UnitedHealth Group for more than a decade. It's a different company after four years with Andrew Witty in charge.

UnitedHealth Group shares rebounded modestly Wednesday following yesterday's crash, with analysts from UBS, Oppenheimer, and Morgan Stanley leaving their ratings unchanged after the health insurer pulled its outlook and announced its CEO had stepped down.

Even UnitedHealth will struggle to overcome parasitic medical costs that Warren Buffett once called a tapeworm eating away at U.S. economic competitiveness. The $300 billion healthcare conglomerate reinstalled Chairman Stephen Hemsley as CEO and yanked its financial guidance.

May 13 (UPI) -- UnitedHealth Group announced Tuesday CEO Andrew Witty will step down, citing "personal reasons." Witty will leave the role of CEO and be replaced by Stephen J. Hemsley, effective immediately.

UnitedHealth Group, the largest health insurer in the country, is turning back the clock in a moment of crisis. On Tuesday, the company announced that chairman Stephen Hemsley is returning as CEO, stepping back into the role he left in 2017.