McCall McPherson explains thyroid testing for people trying to conceive: get a full panel with tight ranges (TSH around 1 mIU/L), check for antibodies, and start prenatal vitamins early. Progesterone should hit 18-23 ng/mL by day 21, and recheck thyroid levels immediately after a positive test.
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This is everything you need to know about your thyroid if you're trying to conceive. First thing, you do need a full thyroid panel if you're trying to conceive, and I like those numbers more narrow. TSH around 1, T4 between 1 and 1.2, free T4, free T3 between 3.6 and 4.2. This matters. It helps you get pregnant. It helps you stay pregnant. Also check antibodies, TPO and thyroglobulin antibodies. In a perfect world, you would already have worked to reduce these. Because that too impacts your ability to get and stay pregnant. Number 2, take a prenatal early. Don't wait to start until you're pregnant. It matters more the year leading up to pregnancy than starting at the moment you get pregnant. So start early, start now. Third, progesterone, y'all. This is key. So many women with thyroid issues have low progesterone, which is the number one risk for miscarriage. So progesterone is what allows us stay pregnant in early pregnancy. I want it between about 18 and 23 on day 21 of your cycle, of a 28-day cycle. Okay, so check it. If it's lower than that, I always start my patients on preventative progesterone. Basically, I want to ensure the moment they get pregnant, if they're actively pregnancy planning, they will be able to stay pregnant. I check their progesterone the day they tell me they're pregnant and I check it every week thereafter if it's low until it shows me that it's right. Lastly, check your thyroid as soon as you get pregnant because increases in thyroid demand happen and they happen pretty early. So we want to ensure that we've increased your medication to support pregnancy.
