John Noseworthy, MD, will step down as president and CEO of Mayo Clinic at the end of 2018 after nine years at the helm of the health system.

In a blog post, Mayo said Noseworthy has been asked to serve another year at the request of its board of trustees. Board chair Samuel Di Piazza said the system’s leaders have typically served eight to 10 years and, while trustees “would welcomed Dr. Noseworthy serving even longer,” it respects his “personal decision to retire.”

With Noseworthy’s exit finalized, the board will begin searching for his replacement.

“Our goal is to identify the next president and CEO by early fall so that the new [president and] CEO and Dr. Noseworthy will have time to work with his successor to ensure a seamless transition,” Di Piazza said. “This process will ensure a transition process focused on sustaining and advancing Mayo Clinic’s values and strong strategic direction.”

Noseworthy tenure at Mayo has seen the system maintain its reputation as one of the best hospitals in the country, being ranked No. 1 on the U.S. News and World Report best hospital list in both 2016 and 2017. There have been controversies, too, such as his comments to employees to give preference to commercially-insured patients over those covered by Medicare or Medicaid.

His retirement will cap a 28-year career at Mayo. Since 1990, he held various leadership positions, including chairman of the neurology department and medical director of development. Outside of Mayo, he served as editor-in-chief of the journal Neurology and is currently the health governor of the World Economic Forum.

“I am truly humbled to serve as president and CEO of this amazing and dynamic organization,” Noseworthy said in a statement. “Every day, I continue to be inspired by the work of Mayo’s staff and how they embody our shared values to care for our patients and advance the field of medicine.”