MARIETTA, Ga. — Republican U.S. Sen. Johnny Isakson announced that he will resign at the end of 2019. 

He said that he will not be able to do the job over the long term "in the manner the citizens of Georgia deserve"

"After much prayer and consultation with my family and my doctors, I have made the very tough decision to leave the U.S. Senate at the end of this year. I have informed Georgia Governor Brian Kemp today that I will resign my Senate seat effective December 31, 2019," Isakson said.

Isakson’s Senate term ends in 2022, and there will be three years left in the term when he vacates the seat in December.

RELATED: Political leaders react to Sen. Johnny Isakson's resignation

Isakson, 74, was diagnosed with Parkinson’s disease in 2013. In July, Isakson fell in his D.C. apartment and suffered four fractured ribs and a torn rotator cuff. On Monday, Isakson underwent surgery at WellStar Kennestone Hospital in Marietta to remove a 2-centimeter renal cell carcinoma from one of his kidneys.

“In my 40 years in elected office, I have always put my constituents and my state of Georgia first. 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," Isakson said. "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."

In 2016, Isakson won re-election with 54% of the vote and became the first Republican in Georgia to be elected to a third term in the U.S. Senate. After more than three decades in the real estate business, Isakson became the only elected official in Georgia to serve in the Georgia House, the Georgia Senate, the U.S. House and the U.S. Senate.

“I look forward to returning to Washington on September 9 when the Senate goes back into session. And 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.”

RELATED: Sen. Isakson crosses party lines, votes with Democrats to end shutdown

In a letter to Gov. Brian Kemp, he said it has been an "honor and privilege to serve the state." 

He added that it pains him to leave in the middle of his term, but he knows it is the right decision for the citizens of Georgia. 

RELATED: Read Sen. Johnny Isakson's resignation letter to Gov. Brian Kemp