Alex Trebek, the longtime host of “Jeopardy!,” appeared on “Good Morning America” on Wednesday for a frank interview about his experience with Stage 4 pancreatic cancer, including his struggle with depression during chemotherapy.

“My oncologist tells me I am doing well, even though I don’t always feel it,” Mr. Trebek said on the ABC morning show.

When Mr. Trebek, 78, announced the diagnosis last month, there was an immediate outpouring of shock and support from fans and well-wishers, whom he thanked on Wednesday. But he said he wanted to use the attention to raise awareness about pancreatic cancer and what it was like to live with the disease.

“I have had kidney stones, I have had ruptured disks, so I am used to dealing with pain,” he said. “But what I am not used to dealing with is these surges that come on suddenly of deep, deep sadness. And it brings tears to my eyes.”