McCall McPhersonFounder, Modern Thyroid Clinic.

Pregnancy Thyroid: How to Optimize T3/T4 Levels #shorts

7 Aug 2025 · 1 min

Watch on YouTube

1:02

A short YouTube monologue by McCall McPherson about optimizing thyroid hormones during conception and pregnancy. The speaker says T3 can help with conception and early pregnancy maintenance, but emphasizes that T4 is the hormone that crosses the placenta and nourishes the fetus, so clinicians should prioritize maintaining maternal T4 (often via levothyroxine/Synthroid) rather than suppressing it to favor T3.

Chapters

I have successfully taken women with infertility a history literally one of them had nine miscarriages and took her through successful pregnancy by optimizing thyroid and hormones to an extent too, right? Progesterone, et cetera. So T3 versus T4 in pregnancy. Right? So to get pregnant, stay pregnant, T3 improves my ability to get patients pregnant to maintain pregnancy, especially early on. Then guess what? We move into an emphasis on T4. If T4 is what nourish nourishes the baby. If T4 is what crosses the placental barrier, the baby's access to T4 in pregnancy takes precedence. So we would never suppress a pregnant woman's T4 in order to give her enough T3. That's not going to happen. Obviously moms who are pregnant value the health and development of their baby. Of course we do too. And so we ensure the entire pregnancy that have access to enough T4 often by supplementing with T4, levothyroxine, synthroid, et cetera.