CHAPEL HILL, North Carolina (CNN) -- Democratic presidential candidate John Edwards and his wife, Elizabeth, have scheduled a news conference for Thursday to discuss what sources close to Edwards described as possible developments with her health.

The sources would not disclose the exact nature of Thursday's announcement, but they did say that the couple is not going before the press to say that "everything is OK."

Elizabeth Edwards underwent treatment for breast cancer after the 2004 campaign, in which her husband was the Democratic vice presidential nominee.

The sources close to Edwards said his wife had a routine follow-up appointment on Monday to check her breast cancer, which was believed to be in remission. According to sources, the doctor called back on Tuesday and asked her to come in again on Wednesday.

Edwards, who was campaigning in Iowa, cut short the rest of his schedule on Tuesday to fly back to be with her. The two of them went to see the doctor together on Wednesday, the sources said.

A blog posting on Edwards' presidential campaign Web site Wednesday evening was entitled, "We love you, Elizabeth."

Jennifer Palmieri, an Edwards spokeswoman, declined comment when contacted by CNN.

It remained unclear whether the developments would have any effect on his presidential campaign. But "don't assume the worst" about the impact of Thursday's announcement, said one of the sources close to Edwards.

The news conference was scheduled for noon in the Carolina Inn in Chapel Hill, North Carolina.

In a December 2004 interview on CNN's "Larry King Live," Elizabeth Edwards expressed confidence in the progress of her treatment for breast cancer.

"I just have a belief that I am going to beat this," she said. "Every indication is that all the news I've gotten really has been good news, so I feel pretty confident. I'm making those plans for the next 40 years."

She also said at the time that her husband would have her full support if he decided to run for president again in 2008.

"I think that he is a unique and powerful voice, and I think that it's a voice that we need on the national stage," she said.

John Edwards, a former senator from North Carolina, announced in December that he would again pursue the Democratic nomination. Among the party's hopefuls, national polls show him running third behind Sens. Hillary Clinton and Barack Obama.

On Tuesday, Edwards campaigned at Iowa's Biomass Energy Conversion Center, where he unveiled a plan intended to achieve energy independence and halt global warming. (Watch Edwards declare global warming a "huge emergency" )

Edwards and his wife met in law school at the University of North Carolina. They married in 1977 and have had four children. Their first child, Wade, was killed in a 1996 car accident.

In her 2006 book "Saving Graces," Elizabeth Edwards wrote about her life, including cancer treatment and the death of her son.