I was diagnosed with this condition mid 40s about fifteen or so years ago. I was completely unaware of it before and imagined it was the onset of the menopause. I can only describe how I felt then, so sluggish, moving was like wading through concrete, my dress sized increased from size 10 - 12 to size 14 -16, I have never got back to my ideal weight. I thought Thyroxine would be a silver bullet, in so much as I would have increased energy levels, but sadly that has never been the case. At present I take a daily dose of 125 mcg, I still feel tired pretty much most of the time and I have to force myself to the gym, not because I enjoy it, but because I feel I must make an effort to raise my energy levels, because when I don't I feel worse.
I read your comments with interest gracesgran, particularly about digestion, mine isn't that good either. Also what you had to say about 300 symptoms, I remember a practice nurse at my doctor's surgery also told me the same thing about the menopause. I had a late menopause and still have symptoms, I believe hypothyroidism can kick in around the same time with similar symptoms thus blurring the lines as to whether tiredness is due to one or the other.
I believe I read somewhere that what we should actually receive to make us feel better, is pig's throxine, rather than the synthetic thyroxine which is what is prescribed although that opinion is not generally endorsed by the medical profession. I'd give it a try, if it gave me some more energy, even if the side effects were snorting and a curly tail, small price to pay 