UnitedHealth Group announced that CEO Andrew Witty is stepping down due to 'personal reasons,' and former CEO Stephen Hemsley will replace him.

Witty will act as a senior advisor to his successor, Stephen Hemsley, who served as UnitedHealth Group's CEO from 2006 to 2017.

UnitedHealth Group Chief Executive Officer Andrew Witty stepped down, effective immediately, "for personal reasons", the company said Tuesday. “Leading the people of UnitedHealth Group has been a tremendous honor as they work every day to improve the health system, and they will continue to inspire me,” Witty said in a statement shared by UHG.