Republican Sen. Johnny Isakson announced he'll resign his seat at the end of the year.
In a statement released Wednesday, the Georgia senator said he's stepping down due to "health challenges" related to Parkinson's disease, as well as a recent surgery. He was diagnosed with Parkinson's in 2013.
In a tweet, Isakson wrote: "It has been the honor of a lifetime serving the state of Georgia. This decision pains me greatly but I know it is the right thing to do."
Isakson is the only person to have served in Georgia's House and Senate and the U.S. House and Senate.
There will be three years left in Isakson's term when he officially vacates his seat on Dec. 31.
Additional reporting from Newsy affiliate CNN.