I spent some time Googling up some information on sub-clinical hypothyroidism (SCH) and pregnancy today. It seems like there is a lot of debate among physicians on whether it needs to be treated or not. Some studies have suggested that SCH does increase the risk for adverse outcomes in pregnancy (though not nearly as much as overt hypothyroidism) and some have found that it doesn’t. This article sums it up pretty well:
Experts agree that overt hypothyroidism should be treated for both maternal and fetal benefit, but whether SCH should be treated is less certain. Although the risks for pregnancy complications and fetal neurologic damage are far from clear, available evidence suggests a possible risk for adverse outcomes. Levothyroxine treatment is relatively cheap, safe, widely available, and well tolerated; however, the 2 prospective interventional trials (ie, Negro and colleagues and CATS) had negative primary outcomes. This leaves the clinician who diagnoses SCH in a difficult position. ACOG recommends against “screening and treating” SCH in pregnancy, but does not directly address the situation if it is found incidentally or by means of risk factors. Other endocrine organizations, such as the Endocrine Society, and the American Association of Clinical Endocrinologists, do recommend treating SCH in pregnancy. Given the lack of clear guidance from the literature, it is reasonable to leave the treatment decision up to the individual physician and patient.
Physicians should exercise caution when interpreting maternal FT4 levels. Method and trimester-specific reference ranges should be used when available. Although some studies have found an association between SCH and pregnancy complications, including increases in abruption, preterm delivery, and pregnancy loss, others have not. Nevertheless, theoretical concern surrounds SCH and the risk for neurologic impairment in the fetus. More studies are needed to confirm and define this risk.
If SCH is diagnosed either by symptoms or by risk factors, insufficient evidence exists either for or against a recommendation for treatment with a low dose of levothyroxine. Universal screening of all pregnant women for hypothyroidism, overt or subclinical, is not currently recommended.
I called my health system yesterday to leave a message for my hot doctor and ask if he knows yet what dosage to put me on, and he managed to call me back just a few hours later. I’m now on 50 mcg of levothyroxine a day. I haven’t heard back on my Free T3 yet.
While the evidence is divided, in my case (and assuming that my FT3 is normal and I really am SCH), I’m glad that we’re treating with a low dose of levothyroxine given how much my TSH has risen in 4 months. Now I can understand why my doctor chose not to treat before I got pregnant, and knowing that my risk of adverse outcomes in pregnancy are much lower than it would be if I had overt hypothyroidism puts my mind at ease.