Trivia: Season 17 had the highest audience viewing figures of any season of Doctor Who. The average audience for Season 17 was 11.2 million viewers. The highest audience viewing figure ever for any individual Doctor Who episode was part 4 of "City of Death" (first broadcast 20 October 1979) with 16.1 million viewers. However, these figures were artificially boosted by the fact that, at the time, ITV was off the air due to a strike, leaving just the two BBC Channels broadcasting.
Trivia: "Shada" is famous amongst Doctor Who fans for being "the show that never was." There were to have been six episodes of the story, scheduled for transmission beginning 17 January 1980. Location filming did take place in and around Cambridge in September/October 1979. However, studio recording was hit by a strike by BBC Technicians in October 1979. When the strike was settled, the BBC studios were all fully booked for other programs, so "Shada" could not be completed in time for its scheduled showing, and so it was never completed. (There was an attempt to make "Shada" the first story of season 18, but by that time, several key people, including writer Douglas Adams, had left, and the story was formally abandoned and cancelled in June 1980).
Trivia: Plot elements from this episode and "City of Death" (the Cambridge don whose flat is a time machine, and Scaroth's mucking with history to prevent the accident that stranded him on Earth) formed the basis of Douglas Adams' novel Dirk Gently's Holistic Detective Agency.
Chosen answer: No, it was the result of the Cybermen's draining Earth of energy to their world, that also affected the Doctor, draining his energy as well, causing him to regenerate.
Also In the episode it's said that his body was wearing thin.
Dan23