So it was Graves

To whomever suggested that my atrial fibrillation might be a sign of a
thyroid condition, thanks. As it turned out, it is Graves disease,
something that the FAA can work with.

One symptom of Graves is increased irritability which, thankfully, has
not been bothering me. Seems to bother everybody else, though. :-)

It also can cause you to lose weight (unfortunately, in my case, I am
experiencing a very rare weight gain -- and will probably gain weight
again in a couple months as the disease is brought under control). At
least my eyes don't bug out like Marty Feldman's (he had Graves). Good
thing, too, or it could cause double vision. It does make me very
sensitive to heat, something which was bothering me a great deal in
the Philippines.

Indications are that the condition is probably not permanent and might
even go away on its own.