The NBC "Today" co-anchor said her family remains devastated and pleaded for anyone with knowledge of what happened to come forward.
"I'm coming on today with a very specific message," Guthrie said in a video posted to Instagram with the caption, "Bring her home," and a yellow heart.
"It has been months since our mom was taken from us. Our family is in agony. We are in a nightmare that will not end," she said.
“The world can be a cruel and unforgiving place, and I know that you have tried to do things the right way. So I’m asking you, begging you to do the right thing now. Make the right choice. Help us find her, tell us where to look for her. I truly believe it is never too late to do the right thing. Help us bring this situation to an end for all of us,” she said.
Nancy Guthrie disappeared during the early morning hours of Feb. 1 from her home in Tucson's Catalina Foothills. Federal investigators are treating the case as a kidnapping.
Surveillance video released by the FBI shows an armed person dressed in dark clothing approaching the home before covering a Nest doorbell camera. Nancy Guthrie has not been found, and authorities have not publicly identified a suspect or announced any arrests in her disappearance.
The Guthrie family is offering a reward of more than $1 million for information leading to Nancy Guthrie. The FBI continues to seek tips through its national tip line, and Tucson-area Crime Stoppers is offering an additional reward for information leading to an arrest.
Authorities have released few public updates in recent months.
Whitney, who covered the case as a Phoenix television reporter, said one alleged message demanded millions of dollars in bitcoin in exchange for Nancy Guthrie's release and included details about the crime scene that had not been released publicly. Whitney also described a second communication that purported to say Nancy Guthrie died shortly after the abduction.
Law enforcement has not publicly confirmed the authenticity of the communications discussed on the podcast.
NTD contacted the FBI and the Pima County Sheriff's Department seeking comment on the communications discussed during the podcast. The sheriff's department referred questions to the FBI. The FBI did not respond before publication.
Anyone with information is urged to call the FBI at 1-800-CALL-FBI or submit a tip online. Anonymous tips can also be submitted through 88-CRIME in the Tucson area.