TTC after thyroidectomy

[Trishlk]

I had my thyroid removed in July because of multiple nodules and cysts and possible cancer, it wasn't cancer we found after the surgery. Anyway, I was on 125 of synthroid after the surgery, then 150, then 137, and now back to 125.
The problem is we are trying to conceive and I am doing the basal body temperatures to chart my cycles. Last cycle, when I was switching from 150 down to 137 I clearly ovulated and my temps were fairly normal, there was a thermal shift. This cycle when I was switching from 137 to 125 my temps were low accross the board, with 97.70 being the highest and 97.20 being the lowest, most are around 97.50. I read that low BBT can be a result of hypothyroidism.
My question is, if my temps were better on the higher dose then why are my blood tests showing that I need a lower does? It seems we are going in the opposite direction.
I have seen that if your TSH is to low you need to lower the dose, but that is hyperthyroidism, and that isn't what causes low temps.
Is it different when the body has no thyroid and is totally relying on synthroid? Is it then the opposite where you lower the dose if you are hypo instead of hyper? Please explain.
Thanks

[Trishlk]

Thanks! I am pregnant now! My doctor increased my dose back to 150 and I am getting blood drawn every 6 weeks now. I am so excited but so nervous at the same time after losing one.

[Trishlk]

Thanks, my last TSH was 0.24 and she is lowering my dose to raise it up. Looks like we are on the right track.

[Mark Lupo, M.D.]

I don't use BBT testing for thyroid disease.  We rely on TSH levels and adjust medications accordingly.  BBT can be helpful to track ovulation but I have no experience with this.  From a thyroid standpoint, the goal is to maintain TSH in the 0.3-2.0 range when TTC and during pregnancy.  During pregnancy the thyroid medication may need to be increased.