For a Time Lord, to be pre-regeneration - that is, having not yet regenerated - was a sign of youth. (GAME: The Heir of Gallifrey [+]Loading...["The Heir of Gallifrey (game)"])
One source stated that Time Lords were born with just one heart and grew a second heart on regeneration. This included the Doctor, who in their first incarnation had only one heart. (PROSE: The Man in the Velvet Mask [+]Loading...["The Man in the Velvet Mask (novel)"]) Other accounts showed Time Lords having two hearts in their original incarnation, such as the Doctor (AUDIO: Frostfire [+]Loading...["Frostfire (audio story)"], The Abandoned [+]Loading...["The Abandoned (audio story)"]) and Jenny. (TV: The Doctor's Daughter [+]Loading...["The Doctor's Daughter (TV story)"]) Tegan Jovanka was under the belief that the second heart of a Time Lord was only developed upon the first regeneration, much to the surprise of Leela, who believed that a Time Lord always had two hearts, with neither being sure who was correct. (AUDIO: Time in Office [+]Loading...["Time in Office (audio story)"])
Klyst assured Louis following his first regeneration that the first was always more painful than subsequent ones. (AUDIO: Unregenerate! [+]Loading...["Unregenerate! (audio story)"])