The chief executive of the Herts Valleys Clinical Commissioning Group (CCG) will leave her role at the end of the year.
Kathryn Magson has headed the organisation, which oversees health across the area, for the last two-and-a half years.
But at the end of this year she will take up the post of interim chief executive of health and social care on the Isle of Man - reporting directly to the government's chief secretary, on secondment.
Commenting on Ms Magson's planned move, CCG chairman Dr Nicolas Small said: " . . . our patients, this organisation, and indeed the system as a whole, has benefited immeasurably from having Kathryn as our chief exec.
"Her impact has been truly transformational and she has been an absolute pleasure to work with.
"Kathryn will leave us with a CCG team and board who have been inspired by her leadership and empowered to continue developing and embracing change.
"As an organisation, her impact will be long lasting - leaving us stronger and well-able to face the challenges ahead."