Just an update, really, after I asked some questions about levothyroxine. I was on 100mcg but feeling no different. On the basis of a suppressed TSH last August, the "specialist" endo told me I was at risk of a heart attack and to reduce to 75mcg. Devastated, as my T4 result was 12.2 (12.0-21). GP #1 allowed me to stay at 100mcg. Last week, I saw GP#2 who said, looking at those results, I clearly need more T4 and should have had it last August. New blood test. My TSH was still suppressed (0.125 or thereabouts I think) but the T4 was 2-something (12.0-21). So VERY VERY low. No T3 tested and "never will be" according to GP#2, lab refuses because, she says, it's such a tiny minority of people with the conversion to T3 problem and that is why they will not test it unless you have an inherited problem.
I hope this means I'll get a hefty increase in T4. I have to go back and see GP#2. GP#2 agreed endo was useless given he told me to reduce my T4, but has now said I need to be referred back to Endocrinology again. I am not sure this is a good plan, given that I have been unwell for 7 years and been seeing an endo for 2 with absolutely no improvement, and, arguably, feeling worse. I just want the GP to give me the increased T4 and see how I get on. Anyway, I just wanted to thank you for your support and I hope things might improve now that the GP finally seems to be realising that I'm under- not over-medicated.