I know MadB knows more about this than I do, but I had elevated TSH levels and my endocrinologist (luckily I had one prior to pregnancy as I have had thyroid issues in the past) wanted to get on top of it as soon as possible (to be conservative, not because it's reason for immediate alarm). I recall having a 2nd series of blood tests and then just being put on Thyroxin (I forget the generic name) - you then have fairly regular blood tests. It's all really no big deal in terms of treatment, you just need to be seen by the specialist. By the way, my only issue was an elevated TSH - and elevated being on the high end of normal whereas best practice for pregnancy is on the low end of normal (I forget the exact threshold). Just as an aside, my TSH levels are still being monitored post-birth most recent results discussed with endocrinologist yesterday and she said - "well, your TSH is still normal but it's going up...are you thinking of trying to get pregnant again in the future" and when I responded "we think so", she told me to start a very low does of Thyroxin again as she wants to see it steady at the right level before we try a transfer (ivf)...which won't be for at least 6 months - if that soon.

Oh - and they only ever focused on TSH for me - I never quite understood why that was.