Mayor Thomas M. Menino’s diabetes -- disclosed during a news conference Monday when he was transferred to a rehabilitation hospital -- was likely triggered by the multiple medical problems he had when he began a month-long stay at Brigham and Women’s Hospital in October, one of his doctors said Tuesday.

Dr. Charles Morris, an internist at the Brigham who helped treat the mayor, said via e-mail that the mayor entered the hospital with an elevated blood sugar level that he believes was exacerbated by the “stress of being sick.” High blood sugar is an indicator of diabetes.