Excuse me if this seems too personal, but do you have a history of heart disease or cancer? What about diabetes or depression? Your doctor is interested in things like that because the answers may determine how he treats you. You are probably interested as well; if you have a close relative who had heart disease you may take extra precaution to make sure you are living a heart-healthy lifestyle.
As an adoptee, I have struggled with questions about my family medical history all of my adult life; there are no easy answers. I've written about that on my Arms of Adoption blog where I am celebrating the publication of a new report published by the Adoption Institute about adult adoptees access to their original birth certificates.