NFL Hall of Famer Forrest Gregg says he has Parkinson's disease

Forrest Gregg, who earned the nickname "Iron Man" for playing in a then-record 188 consecutive NFL games during his Hall of Fame career, tells The Associated Press he's been diagnosed with Parkinson's disease.

Although the cause of the debilitating neurological disorder is unknown, Gregg, his family and his neurologist say his disease may be related to numerous concussions he suffered during his playing career in the 1950s at SMU and from 1956-71 with the Green Bay Packers and Dallas Cowboys.

The 78-year-old Gregg was diagnosed last month after being referred to Dr. Rajeev Kumar, a Parkinson's expert and medical director of the Colorado Neurological Institute's Movement Disorders Center in Denver.

Gregg's symptoms include hand tremors, a stooped posture, shortened stride and softened voice.