Thyroid function is critical to successful conception, healthy pregnancies, babies and mum’s post-partum wellbeing, so we need to take the time to ensure we’re monitoring it properly.
First of all you need the right tool for the right job & that means we need trimester specific reference ranges – which unfortunately many pathology companies don’t use in Australia. Due to the thyrotropic action of HCG (acting a bit like TSH), TSH should actually decrease in the 1st trimester and while TSH is less affected in 2nd and 3rd trimesters it should still actually sit lower than in non-pregnant females. So that’s the biggest lesson right there – to illustrate the point a TSH> 2.5 mIU/L in the first trimester is an instant red flag for most endocrinologists, who at the very least would want to monitor that patient’s thyroid function very closely (e.g. monthly throughout the 2nd trimester). And what do we do about women who enter pregnancy with detectable thyroid antibodies but no overt thyroid disease? Does it matter….absolutely!..the correlation between the presence of TPO antibodies and higher rates of miscarriage and poor pregnancy outcomes is consistent, not to mention them being a strong prognostic indicator of post-partum thyroiditis.
If you’re working with pregnant patients you should read the updated American Thyroid Association Guidelines (not the whole 46 pages…just skip to the interesting bits!) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3472679/ and then a slightly scathing attack of these same guidelines by Pop published last year – but good naturopathic food for thought: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4216983/
Bit obsessed with thyroid right now…but this too shall pass….;)