I have hypothyroidism. I was on too low a dose of thyroxine for a long time and really had to fight to get my dose upped. I used to get so tired i had to go back to bed in the afternoon on a lot of days. My dose was increased from 50mcg to 75mcg and later to 100mcg and now I'm fine. This wouldn't have happened if I hadn't kept on at my doctor and insisted on seeing an endocrinologist. The trouble is, if your results come back in the 'normal range' the doctor will not do anything. However, some people need to be at the top end of the 'normal range' to feel well, and that was me. So I'd suggest anyone who has tested in the 'normal range' but feels they may still be hypo get a copy of their blood results and keep being a pain in their doctor's backside till they get a satisfactory result.
Being adequately medicated hasn't made me any less Aspie, however! 
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*it's been lovely but I have to scream now*