I was diagnosed with an underactive thyroid a few months ago. I've just been put up to 75mg from tomorrow. I was wondering whether it's possible for symptoms to vary so that they can be worse one day than the next? My reason for asking is that today I am absolutely freezing, I feel exhausted (even though I had a decent sleep last night), I can not concentrate. I just went to the gym and I had no energy at all. I feel much worse today than I normally do. What complicates this is that I'm also recovering from post-natal depression, so it might be that. However, my 'blips' with the depression tend to feel different. I have a much lower mood than I do right now, and I generally don't feel this exhausted. There's also no difference in my sensitivity to cold. Any ideas?