Just wanted to add to this discussion Katieferg81 and give you my story...
I had a horrendously underactive thyroid, discovered after six months of ttc-TSH of 31.5!! Not sure how I didn't realise, had been feeling rough for a long time but thought I was just stressed. Anyway, my TSH was at 0.54 after medication so I thought great, I will conceive now. But alas, we remained unable to get pregnant for two years after that. I had every test done and all came back great, including my AMH which was good for my age (36 at the time).
I had IVF once via NHS, our one and only free go, and I had a chemical pregnancy. NHS consultant believed it was because of my age and he also told me I was overweight (THAT was a very low point...old and fat, thanks very much!)
Then we went to CARE Sheffield and the consultant recommended that I get the antithyroid antibody test done. Turned out I had a very high number, over 1500 when it should be about 50. This meant that I had (and still have) an autoimmune thyroid disease. The explanation was that I had so much inflammation in my body that an embryo wouldn't survive. They treated me with IVF and steroids and I now have a 9 month old.
The reason I am telling you all this is that people can have the autoimmune response going on in their body and their TSH levels can be fine. TSH is only one part of the story...My message is if you feel a bit off or have any symptoms such as:
-Constipation
-Hair loss
-Feeling cold
-Low mood
-Fatigue
-Brain fog
-Dry skin
-Joint pain
Request an antithyroid peroxidase antibody test. That might give you more of a picture. Also full bloods: ferritin and all the vits. My GP was good and did those tests but some are a little less generous.
If you want to know any more about autoimmune thyroid stuff I have a gazillion links to articles etc. so just let me know.