Fletcher showed none of the traditional symptoms, and had in fact been tested several years ago. He had an off again/on again limp.
X-rays were clear, VF negative, but my vet said his thyroid was lower than it had been, and thyroid problems can cause neurological problems, so we started him on the meds. It seems to have helped.
All that said, if he has no other issues than a bald butt, I probably wouldn't bother.