WZ, at about the same point post-rad, I felt a decrease in energy and had thyroid tests done. What they showed was a surprising increase (hyper) which would tend to explain why I have been eating like a linebacker and gaining no weight, a situation much to my liking (grin). Subsequent testing has shown the levels to be falling towards normal. The explanation I was given is that the chemo I had was still affecting my body. My rad oncologist told me hypothyroidism generally shows up at about 2 years out, for what that's worth. I would recommend that you request testing. Good luck!
Joanna
P.S. My energy returned to previous Type A levels in a couple of weeks, so I think maybe I just had a bug.