Symington also resigned from her role as chair of the Humber and North Yorkshire Health and Care Partnership ICS.
The former chair, who left last week, said the decision had been ‘incredibly difficult'.
She added: ‘It has been a privilege to lead our Integrated Care Board and the wider system for the past three years.
‘I am immensely proud of the work of the ICB and the partnership during my time as chair. Together, we have made significant strides towards our goal of improving the health and longevity of our population, working to narrow the gap in healthy life expectancy between our communities by 2030 and increasing life expectancy by five years by 2035.
‘Achieving real change can only happen through collaboration across our health and care system. I was particularly pleased when NHS England commended the ICB for its strong leadership and collaborative efforts with our system partners.'
An ICB spokesperson said Symington's decision was not related to last week's announcement of NHS reorganisation and spending cuts.
ICB vice chair, Mark Chamberlain, is taking over as interim chair.