Lyles went missing around 12:30 yesterday after leaving for an afternoon walk from his home at Marina Village in Grand Rivers in Livingston County.
Family members became concerned when Lyles did not return from the walk and searchers later began an extensive ground and water search.
Lyles has been receiving treatment for a serious medical condition and according to family and friends needs medication, which he left at home along with his identification and cell phone.
Curt Curtner, Chief of the Marshall County Rescue Squad, said agencies from throughout the area were on the water searching until after midnight last night. They returned at around 8 this morning.
Curtner said agencies from Livingston, Lyon, McCracken and Marshall Counties are searching an area around the Canal Campground in Livingston County, just below Barkley Dam.
The Livingston County Sheriff's Office is advising members of the public who wish to assist in the ground search to come to the Canal Campground boat ramp area. Curtner said about a dozen people showed up this morning to help.
Anyone with information on Dr. Lyles is asked to contact the Livingston County Sheriff's Office at 270-928-2122. Lyles was last seen wearing a green shirt and khaki shorts.