Matt Millen is stepping away from his Big Ten Network broadcasting responsibilities for the remainder of the season to concentrate on his treatment for amyloidosis.
Millen, 60, had served as a color analyst for the first five games of the season with play-by-play partner Kevin Kugler.
"We will certainly miss seeing Matt this fall, but his health is the clear priority for everyone involved," Big Ten Network senior vice president Mark Hulsey said in a statement Wednesday. "And we plan to support him in any way possible."
"I am really going to miss my partner," Kugler wrote on Twitter. "Please keep Matt and his family in your prayers."
Millen revealed his diagnosis earlier this year to The Morning Call of Allentown (Pa.). In April, the newspaper reported Millen's heart was working at 30 percent capacity.
The Mayo Clinic describes amyloidosis as "a rare disease that occurs when a substance called amyloid builds up in your organs. Amyloid is an abnormal protein that is produced in your bone marrow and can be deposited in any tissue or organ."
Millen was the Detroit Lions' general manager when the team went 0-16 in 2008. He was fired after that season.
Millen starred at Penn State and captured four Super Bowl titles during his 12-year NFL career as a linebacker with the Oakland Raiders, San Francisco 49ers and Washington Redskins. After his playing career, he spent several years as an NFL color analyst before serving as general manager of the Lions from 2001-08.