hyperthyroidism
I know of 2 airline pilots with previous history of hyperactive thyroid leading to Graves Disease. One had the thyroid surgically removed and the other had radio iodine therapy. Their conditions stabilised sufficiently for them to return to airline flying. The one with the thyroid surgically removed had to take thyroid hormones for the rest of his life. The more fortunate chap who had radio iodine therapy need no further medication. I can't tell why but his thyroid was not totally destroyed and it still produce sufficient thyroid hormones to sustain normal function. Hope this info helps. Good luck...Jetney