Adult Onset Type I Diabetes

I am a 44yr female.  Was diagnosed 2 yrs ago with type I.  I also suffer from hypertension and hypothyroidism.  Several years ago a small, insignificant pituitary tumor was found.  I am not overweight, relatively fit and have no family history of diabetes.  I was wondering if the pituitary is the cause of these issues.  When I inquire, I am told that I am just unfortunate and my doctors cannot give me a reason why I have these issues.  Most importantly, I am interested in finding an underlying reason to the diabetes.  It doesn't seem reasonable that I developed it out of the clear blue sky for no apparent reason.  Can you help?