Alex Trebek is facing a setback.

Last month, the longtime Jeopardy! host announced he had completed treatment for his stage 4 pancreatic cancer. But, while speaking with Good Morning America on Tuesday, the 79-year-old revealed his health has since taken a turn.

"I was doing so well and my numbers went down to the equivalent of a normal human being who does not have pancreatic cancer, so we were all very optimistic," he told T.J. Holmes. "I lost about 12 pounds in a week and my numbers went sky high, much higher than they were when I was first diagnosed. So the doctors have decided that I have to undergo chemo again and that's what I'm doing."

The treatment, he admitted, takes a toll on him physically. "Occasionally, it will cause excruciating pain in my lower back," Trebek shared. "Other times, it's fatigue. Other times, it's nausea. It varies. Cancer is mysterious in more ways than one."

The diagnosis has been hard on him emotionally, as well.

"There are moments when, for no reason at all, I feel this surge of sadness, depression," he added, "It doesn't last very long, but it just takes over my whole being for a short period of time. I understand it more now so I can deal with it a lot better than I did before...I know it's part of who I am and I'm going to just keep going."

After all, he is a fighter through and through. "The thing that I suppose that gives me the most optimism is that, hey, I'm still here," Trebek said. "I don't feel terrible."

Still, he is prepared to say goodbye when his time comes. "I realize there is an end in sight for me, just as there is for everyone else," the beloved TV personality said. "One line that I have used with our staff in recent weeks and months is that when I do pass on, one thing they will not say at my funeral is, 'Oh, he was taken from us too soon.'"

"I've had one helluva good life and I've enjoyed it," Trebek continued. "The thought of passing on doesn't frighten me. It doesn't. Other things do. The effect it will have on my loved ones. Yes, that bothers me. It makes me sad. The thought of myself moving on, hey folks, it comes with the territory."

Still, he remains eager to come to work every day. "As long as I can walk out and greet the audience and the contestants and run the game," he concluded, "I'm happy."

In March, Trebek shared that he had been diagnosed with stage 4 pancreatic cancer.

"I'm gonna fight this," he said in a video clip. "I'm gonna keep working, and with the love and support of my family and friends and with the help of your prayers also. I plan to beat the low survival rates statistics of this disease. Truth told, I have to. Because under the terms of my contract I have to host Jeopardy! three more years!"

Our thoughts are with Trebek and his family during this time.

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