OK, you gave me an idea:
Dear Uncle Sam:
At my age, weight, and general state of physical ineptitude, I am still ready to be involuntarily conscripted into the medical corps, though if I knew such was possible I never would have gotten married and had 3 kids.
By the way, what's a "Cuboid"? And I'm assuming you'll be paying off my $200,000 in student loans while I serve, of course, as well as supporting my wife and children (and inlaws, who I care for in the apartment over my office, and who will be homeless since I otherwise couldn't pay my office mortgage on a military salary.)
Always willing serve,
Sincerely,
Your loyal nephew,
Dr. Polycarp