That's interesting, I wonder why that is? (And I don't think I actually know any more than you Bulie)
My endocrinologist told me the TSH doesn't matter in first trimester as the feotus doesn't have a thyroid to be affected by it, but T4 levels may affect pregnancy.
Anyway, my first pregnancy I had the endo, OB and GP all telling me different things about where my levels shoudl be... 2nd time round I just figured it out for myself.

Anyway, I think the upshot here is follow it up and reassure yourself that it's ok.