Senate Veterans’ Affairs Chairman Johnny Isakson announced Wednesday that he will resign from Congress at the end of this year, citing a host of health issues.

“In my 40 years in elected office, I have always put my constituents and my state of Georgia first,” Isakson, R-Ga., said in a statement. “With the mounting health challenges I am facing, I have concluded that I will not be able to do the job over the long term in the manner the citizens of Georgia deserve.”

“It goes against every fiber of my being to leave in the middle of my Senate term, but I know it’s the right thing to do on behalf of my state.”

Isakson, 74, was diagnosed with Parkinson’s disease in 2013, but opted to run for re-election in 2016 despite the illness. In July, he was hospitalized for fractured ribs and a torn rotator cuff after a fall in his Washington apartment. This week, Isakson underwent surgery in Georgia at WellStar Kennestone Hospital in Marietta for kidney cancer.

He is a Georgia National Guard veteran who left the service as a staff sergeant after six years. After a career in real estate, he spent six years in the House before his election to the Senate in 2005, and has been chairman of the veterans committee since 2015.

In that time, he has been a key figure in all legislation related to veterans policy on Capitol Hill. Up until his fall, he held regular meetings with VA officials and veterans on a host of policy priorities, most notably the implementation of the new Mission Act.

In recent months Isakson had been seen using a wheelchair to navigate the halls of Congress, but still stopped frequently to speak with reporters and staffers.

In a letter to Georgia Gov. Brian Kemp, Isakson said the decision comes “after much prayer and consultation with my family and doctors” and that “I will do everything we can to help whomever you appoint to serve in this seat.”

Isakson is the only elected official in Georgia history to serve in the state’s House of Representatives, the state Senate, the U.S. House and the U.S. Senate.

Despite his ailments, Isakson said he plans on returning to Capitol Hill next month to finish out the remainder of the year.

“After December 31, I look forward to continuing to help the people of Georgia in any way I can and also helping those who are working toward a cure for Parkinson’s,” he said.