“Thyroid in Pregnancy Part Two: Hyperthyroid and Graves” – with Dr. Samantha Do

Dr. Fox: Welcome to today’s episode of “Healthful Woman,” a podcast designed to explore topics in women’s health at all stages of life. I’m your host, Dr. Nathan Fox, an OB-GYN and maternal-fetal medicine specialist practicing in New York City. At “Healthful Woman,” I speak with leaders in the field to help you learn more about women’s health, pregnancy, and wellness. All right. Dr. Samantha Do, welcome back to the podcast. How goes it?

Dr. Do: Goes well, Dr. Fox. Thanks for having me.

Dr. Fox: I love that you call me Dr. Fox on the podcast. That’s awesome. So, yeah, this is, like, our two-part thyroid podcast situation. We did one with Shari Gelber on hypothyroid, and today, we’re gonna do hyperthyroid. Since those words sound alike, they sometimes get confused. And we did the thyroid overview with Shari before, so we don’t have to do that again. But hyperthyroid is a really interesting phenomenon in pregnancy and that a lot of people think they have it or get told they have it, but they don’t really have it. What’s going on there?

Dr. Do: A lot of the symptoms in physiology overlaps with some normal pregnancy physiology. So, the thyroid is stimulated by the hCG hormone, the pregnancy hormone, in mild amounts in normal pregnancy. And so, people can have a transient first-trimester normal appearance of having a little bit of a low thyroid-stimulating hormone because the pregnancy hormone, the hCG, is taking on that role.

Dr. Fox: Yeah. I mean, what we were saying last week with Shari, is that, you know, the hypothyroid is people sort of feel a little sluggish, for lack of a better term. They’re kind of slow, they feel like they’re gaining weight, they don’t have energy, they’re tired, you know, things like that. And hyperthyroid is they feel a little hyperactive or a little jittery in a sense.

Now, obviously, beginning of pregnancy, a lot of women are zonked and they’re very tired. But the other things like your heart is racing, you’re hot, you’re sweaty, things like that which are common in the beginning of pregnancy are also the symptoms of hyperthyroid. So, there’s overlap in terms of, like, the symptoms, and like you said, there’s also overlap with some of the blood results because what is strange is that TSH that we spoke about last week, the thyroid-stimulating hormone that comes from the brain looks nearly identical to hCG.

And so, the hCG, which is a pregnancy hormone, can actually act directly on the thyroid, sort of mimicking the TSH, the thyroid thinks it needs to get stimulated. So, it’s sort of hyperactive. And then because that feedback loop we spoke about last week and then turns off the natural TSH. And so, not only are their symptoms are the same, but if you start doing blood tests on people early in pregnancy, they might appear a little hyperthyroid. And that often gets misdiagnosed.

Dr. Do: Especially for moms that can have higher pregnancy hormone levels of that hCG, anything that raises the hCG level can then make moms look a little bit more hyperthyroid even when they’re not. So, things like having twins where you have extra pregnancy hormone or things like having kind of abnormal pregnancies with hyperemesis when you have more pregnancy hormone or molar pregnancy strain, the kinds of pregnancies where you have more pregnancy hormone can then look more like that hyperthyroid state.

Dr. Fox: Yes. I guess the first sort of takeaway lesson for someone if either you’re pregnant, you know someone’s who’s pregnant and you’ve never had a thyroid issue in your life, you’re perfectly fine, you’re perfectly healthy and then you’re in the beginning of pregnancy and someone tells you, “You have hyperthyroid, like you have a new medical condition related to your thyroid,” saying it’s too fast, double-check that. You know, ask, “Are you sure? Do I really have the condition, or am I just pregnant?” Because that does get missed sometimes.

And then people sometimes get sense, they start getting treated, and we’ll talk about why that’s an issue. You know, true hyperthyroidism is actually pretty rare. Most people don’t walk around with it. It’s far less common than being hypothyroid, which we spoke of last week, which is pretty common to be hypo or subclinical. And so, how would someone know potentially if they really had hyperthyroidism?

Dr. Do: So, some of those symptoms would lead to them getting a workup. And some of those are those fast heart rates, feeling sweaty. Sometimes people actually can have changes in how their eyes look, where their eyes pop out a little bit more, or kind of changes in their skin of their legs where they have kind of scalier skin of the legs. And then blood tests is the absolute way to make the diagnosis.

Dr. Fox: Yeah. When you’re not pregnant, you should not have low TSH and high thyroid free T4, as we were saying. That really shouldn’t be the case when you’re not pregnant. If you are pregnant, it’s sometimes hard to make the diagnosis. Like, if someone says, “Well, I have these symptoms before pregnancy,” and you get the blood test, you have to sort of decide is it real or is it pregnancy.

And some of that’s based on when the symptoms started and some of it’s based on how bad the blood results are, meaning if you’re pregnant and your TSH is super low and your free T4 of the thyroid is super high, then it’s probably real, versus if it’s just slightly high. And there is also, like, there’s a concept with hypothyroid that you could have what we call subclinical. There’s also a concept of subclinical hyperthyroid. And what’s that?

Dr. Do: That’s when you have a low suppressed TSH. So, it’s lower than we would expect, but your thyroid hormone, your free T4 is in the normal range.

Dr. Fox: Right. And as far as we know, that means nothing, particularly in pregnancy.

Dr. Do: Yes. And there are problems with treating it because that overtreating it could lead to less thyroid hormone present for babies’ brain development.

Dr. Fox: Right.

Dr. Do: So, we don’t wanna overtreat subclinical hyperthyroidism.

Dr. Fox: So, let’s say someone truly has hyperthyroidism, why do we care during pregnancy? Like, what’s the problem?

Dr. Do: True hyperthyroidism, thankfully, is rare, but there are true real adverse effects on pregnancy where we worry about increased risks of babies not growing as well, we worry about increased risks of pregnancy loss, miscarriage, we worry about preterm delivery, and then we worry, in rare cases, of baby actually becoming hyper or hypothyroidism.

Dr. Fox: Yeah. So, hyperthyroid is one of the… Like, when we’re learning, you know, we’re studying for OB-GYN and for maternal-fetal medicine, it’s one of the really fascinating conditions because it not only can affect the mother, which can then affect the pregnancy, things, you know, like preterm birth or preeclampsia, you know, miscarriage, but it also is a condition that can directly affect the baby, which is very unusual, meaning most medical conditions that the mother has, the only way it affects the baby is sort of secondary.

Like, if the mom has high blood pressure, right, it can affect the pregnancy, it can affect the placenta, lead to abruption, whatever, you know, growth restriction because the placenta’s not working. But there’s nothing about, like, the high blood pressure directly damaging the baby or causing high blood pressure in the baby. It just doesn’t exist. That’s true for pretty much everything. But for this, there is a situation where it can affect the baby directly. So, how does that happen? Like, what are we talking about here?

Dr. Do: Ninety percent of hyperthyroidism is caused by something called Graves’ disease. And with Graves’ disease, they’re actually antibodies that attack mom’s thyroid, and those antibodies can also cross the placenta and cause problems for baby’s thyroid. And so, those antibodies can make baby hyperthyroid and then sometimes the treatments for mom can make baby hypothyroid.

Dr. Fox: Yeah. That is one of the really odd parts about this where when we’re seeing someone in their hyperthyroid, it actually matters not only that they’re hyperthyroid, but why are they hyperthyroid? And like you said, the majority of times people are hyperthyroid, it’s an autoimmune condition where these antibodies attack the thyroid but they attack it in a way, not that it destroys it, but attack it in the way that it stimulates it. We actually call them thyroid-stimulating antibodies or immunoglobulins.

And so, they sort of cause your thyroid to go into, like, stepping on the gas, right, and they just go into full gear. And so, that if causes the hyperthyroid, eventually, your thyroid can sort of burn out. Like, people with Graves’ disease can have hyperthyroid and then later become hypothyroid, which is another fascinating thing. But initially, it’s fast.

But those antibodies can also, totally separate from the fact that it’s stimulating the mom’s thyroid, can go and stimulate the baby’s thyroid because those antibodies can cross, like you said, the placenta, and go to the baby and make the baby hyperthyroid. So, how will we know if this unborn baby, this fetus, is hyperthyroid?

Dr. Do: We can see signs when we’re monitoring baby on ultrasound and based on heart rate. One of the first things we can see that’s not easy always to detect but is an enlargement of baby’s thyroid gland. So, on ultrasound, we can see either a goiter or a larger size of baby’s thyroid, and that can predate seeing what is another change we can see of baby having a fast heart rate. Like, moms with hyperthyroidism have fast heart rates, babies can have a faster than normal for babies’ heart rate.

Dr. Fox: Right. And again, that is from the antibodies, it’s not from the thyroid itself, meaning if let’s say someone was hypothyroid and they were taking the thyroid replacement frequently called Synthroid, even though there’s other brands. but if you’re taking that and you took a lot of it, the mom would be hyperthyroid because she took too much medication, but nothing would really happen to the baby because that doesn’t affect the baby.

And also, what’s interesting is let’s say mom has Graves’ disease and has all these antibodies, but either her thyroid is burnt out and it’s not fast anymore, or she had surgery to remove her thyroid and so the thyroid’s not there so that mom cannot have hyperthyroid, but since the antibodies are still present, the baby could be hyperthyroid. And so, this is one of those things where we really…we have to sit down and think, you know, we gotta look at her thyroid situation, her antibodies, and the baby, and it really is one of the situations where we’re, like, literally treating two patients and sometimes in opposite directions.

Dr. Do: And why it’s important to know why moms are hypothyroid because sometimes moms have been treated for Graves’ disease, end up hypothyroid, but still have those antibodies. That can cause problems.

Dr. Fox: We said that the most common cause, this was last week, the most common cause of hypothyroid would be a different antibody called Hashimoto’s hypothyroidism, where the antibodies slow down the thyroid. Those do not seem to affect the baby, which is interesting.

But like you said, if someone just walks in and they’re hypothyroid and we don’t know why, we usually have to ask a history, “Well, did you used to be hyperthyroid, has your thyroid been removed, did someone operate on it, did someone give you, like, radiation to it or radioactive iodine to it or have you…you know, did you used to have these symptoms?”

And so, we have to sort of figure it out. And sometimes when we don’t know, we’ll send those stimulating antibodies just to see if they’re there. It does require some expertise to know this and it’s not something that’s common or routine, and we’re, like, a little bit in the weeds here, but that’s what we do. I mean, this condition definitely gets in the weeds. Why else, other than Graves’ disease, might the mom be hyperthyroid?

Dr. Do: The rare causes for mom to be hyperthyroid or sometimes if mom has a nodule on her thyroid, that’s an active nodule that’s leading to more secretion of thyroid hormone. Other reasons why mom could be having hyperthyroid situation are if she has thyroiditis or kind of inflammation picture, meaning the extra thyroid hormone. And then some reasons that we already touched on that aren’t really hyperthyroidism but mimic it are just pregnancy with the elevated hCG, pregnancy exacerbation conditions like hyperemesis, or molar pregnancies.

Dr. Fox: Yeah. And it’s interesting when you said earlier the symptoms of hyperthyroid, one of them you talked about which is these classic features of someone’s eyes, like, normally, if someone opens their eyes and you look at them and you see the whites of their eyes, you only see the whites of their eyes sort of from, like, 2:00 to 10:00, right? If you look closely at someone’s eyes between 10:00 and 2:00, you really don’t see the whites, you just see the color parts of their eyes. And that’s pretty typical.

But there’s a classic thing when people have Graves’ disease that those antibodies that attack the thyroid also attack behind the eyes and sort of push your eyes out. And so, if someone opens their eyes and you see white all the way around their eyes, it might be a sign, not always, some people just have that, but it might be a sign that they have these antibodies. But it’s not from the thyroid, it’s not from being hyperthyroid, it’s from actually those antibodies. So, that is sort of specific to what we said Graves’ disease, but that is the most common cause of it.

So, let’s say someone comes into pregnancy, and I’m gonna give you two scenarios. The first scenario is they come in and they have some of the symptoms and maybe they’ve been misdiagnosed as hyperthyroid when, in fact, it’s just a pregnancy thing. Or we say, “You know what? You’re pregnant and you have a little bit of the hyperthyroid symptoms, you know, your TSH is a little low, whatever it is,” what would you do for her? Right? You don’t believe she has Graves’ disease, you don’t believe she has true hyperthyroidism, she just has some of the symptoms and some of the maybe blood test abnormalities, but you’re pretty confident it’s pregnancy. How would you handle that situation?

Dr. Do: I would reassure her that she’s not at increased risk of the things we talked about like baby becoming hyperthyroid or some other complications like preterm birth or growth restriction. And then I’d recheck her thyroid studies in the second trimester to see that they were improved or different because we’d expect kind of with the profile of hCG peaking at 8 to 12 weeks and then going down, that some of that stimulating effect on the thyroid would be less and certainly wouldn’t get worse. And I wouldn’t give her antithyroid medications.

Dr. Fox: Right. And so, frequently, like, if we see them ourselves for pregnancy, we usually just, first of all, we probably don’t even check the thyroid and then we just let ’em be. But it’s one of the easier consultations we get someone coming to us for hyperthyroid in the first trimester and we quickly determine they don’t have it. We say, “All you need to do is a blood test in a month.” And we’re like, “That’s it.” We’re like, “That’s it. Go home. You’re good.”

So, that’s an easy one. All right. Now let’s say someone comes in and they have Graves’ disease. They have a real hyperthyroidism, they had it before pregnancy, or you conclude that they had it before pregnancy, how would you handle that situation?

Dr. Do: I’d wanna treat them in pregnancy to decrease some of the adverse effects of Graves’ disease in pregnancy, but not overtreat them to take away thyroid hormone from baby. So, we usually, in the first trimester, give them a medicine called PTU that acts to blocks synthesis and release of thyroid hormone from the thyroid. And that can have some rare complications for moms and a slight increased risk of birth defects, but we think it’s a better medication than the other medication in the first trimester, which has more risk of birth defects with this methimazole.

Dr. Fox: Yeah. I mean, these medications… I mean, overall, they tend to be pretty safe and the PTU might be slightly safer, but explain to me what you’re saying that you are gonna treat them, but you’re concerned about potentially the effects on the baby’s thyroid. So, let’s break that down. What about the medication could affect the baby?

Dr. Do: So, the medications both do cross the placenta. And so, they can have some really rare risks of birth defects, but that’s only the first trimester. The thing that it also could affect the baby is it could make baby hypothyroid or lead to a congenital hypothyroidism because baby doesn’t have as much synthesis or development of thyroid hormone, which can then have effects on baby’s development. Baby needs thyroid hormone for kind of normal development and making them hypothyroid and would have adverse effects for them.

Dr. Fox: Right. So, it’s interesting because, again, if you have a situation where mom is hyperthyroid and baby is not, baby is what we call euthyroid, sort of normal, and you give the mom the medication to fix her thyroid, to lower it, that’ll work, but at the same time, you’re gonna lower the baby’s thyroid potentially into the hypothyroid state, and you can’t really treat that.

So, we know this. And so, it’s always a concern when someone’s hyperthyroid and we start treating them, are we gonna be in our effort to help the mother, which is good because we don’t want her to have the preeclampsia and, you know, growth restriction and preterm birth, but are we now directly sort of affecting the baby? And so, it’s a really interesting thing that we basically give them, like, as little as humanly possible. And our goal is not to sort of get that lab result smack in the middle of the range, which is sort of, like, what you would expect.

We wanna keep it, like, at the very edge of normal and even slightly abnormal, just enough that we think it’s gonna keep her from having bad symptoms and keep her safe and maybe affect, in a good way, the risks of the pregnancy, but just, you know, give as little as possible because we don’t wanna affect the fetus.

And it’s interesting because it’s sort of the exact opposite of what we do with hypothyroid where we were saying last week, “Yeah, treat. It’s not a big deal. What’s a big deal if you get a little bit of thyroid? You don’t need it. Give ’em a little more. Like, it’s probably not an issue.” But for this, it’s the exact opposite. We’re very cautious to give, like, the minimal dose necessary, which is exactly why, like you said, if someone doesn’t need it at all, we don’t give it. Like, we really hold back on this. It’s not something that you want to take if it’s borderline. You wanna actually wait if it’s borderline. And that’s a balancing act.

Dr. Do: It’s definitely a balancing act where we sort of ignore the TSH value, the thyroid-stimulating hormone, we expect it, and we actually want it to be still too low…

Dr. Fox: Right.

Dr. Do: …just to maintain their thyroid hormone level at the upper end, like you’re saying, of normal or even a little bit above so there’s enough thyroid hormone crossing the placenta to help baby.

Dr. Fox: Right. Now, let’s say someone is listening to this podcast, and they’re like, “Wait a second. I got hyperthyroid and I didn’t know that this medication’s not so good for the baby. I don’t wanna take it at all. Like, don’t give it to me. I don’t mind having my heart race, I don’t mind sweating, I don’t mind my blood pressure going up. I’ll even deal with a little bit of preterm birth, whatever it is. I don’t wanna, you know, affect my baby at all.” Why would we prescribe it? Why would we still say, and I know you’re gonna say it’s a good idea, why would we still say it’s a good idea? Like, what’s the problem with not being treated at all for hyperthyroid?

Dr. Do: The risk is that there can be severe effects for mom in terms of her health and which then translate into severe effects for baby. So, growth restriction, extra risk of preeclampsia, preterm birth, those are adverse outcomes, but not a true clinical emergency…

Dr. Fox: Right.

Dr. Do: …as opposed to the two things that we worry about where mom, because of excess thyroid in pregnancy, gets a cardiomyopathy or a heart condition that’s detrimental and risky for mom’s life or something called thyroid storm where there’s so much thyroid hormone around that mom goes into this hypermetabolic state that’s really dangerous.

Dr. Fox: Right. Our listeners might not know this, but I know this, that just saying the words thyroid storm has caused Dr. Do’s blood pressure to shoot up and her pulse to go up because thyroid storm is not only something that’s terrifying when you see it as a doctor. Obviously, if you’re the patient, that’s pretty bad too. But as someone who has to take their boards for maternal-fetal medicine, it is always, “Oh, my God. They’re gonna ask me about thyroid storm. This is a disaster,” because it is, like, classically asked, and it’s complicated. So, what is thyroid storm? It sounds like the name of a movie, like you know, “Thyroid Storm” starring George Clooney or whatever it is. What happens?

Dr. Do: It would be an exciting movie because it’s dramatic. Moms have really fast heart rates and they can have arrhythmias or regular heart rates. They are sweaty, they can have fevers, they can have seizures, they don’t feel well, their heart cannot work as well, and it’s because of all this excess thyroid hormone around. It’s one of those true emergencies where moms need to be in the ICU and need to be treated promptly.

Dr. Fox: Yeah. I mean, I’ve seen it a few times in my career, and it’s pretty scary. I mean, thyroid storm is literally life and death, and it’s like they go into intensive care for a reason. I mean, everything can shut down, and we treat it aggressively. And you have to… I mean, there’s a whole bunch of things you have to do, which is why Sam’s getting palpitations here over what are the things we have to do, and how do I answer them on the oral examination, and all that stuff. But, yes, there’s a lot of things that have to get done.

And so, this is something that we are very, very worried about if someone has real hyperthyroidism. And so, essentially our treatment is, like, first and foremost, to prevent her from getting that, right? And so, if someone’s at risk for that, we’re gonna absolutely recommend be on medication because that’s really bad for her and obviously consequently really bad for the baby.

And then it’s sort of a balancing act. How much do we need to give her to prevent those other things we’re talking about to go through extra risk and preeclampsia? No one knows for sure, but that is a big one. And the heart failure’s another thing, right? People’s hearts sometimes are not ready for all that work. Pregnancy alone is a lot of work and adding hyperthyroid to pregnancy untreated can be bad. So, it’s really, you know, the message is we definitely don’t wanna treat someone who doesn’t need it, but if you need it, you need it.

Dr. Do: We definitely wanna treat people who need it because I have not seen it in people well treated although there’s some triggers that can cause it to come up. But untreated, that’s a big place.

Dr. Fox: Yeah, yeah, yeah. Typically, if it happens, it’s someone who either doesn’t know they have hyperthyroidism in the first place or, for some reason, they or their doctor has chosen not to treat them in pregnancy and it backfired. So, yeah, that is a reason to do it. That’s for the mom.

Now, what if we have a situation where mom is not being treated for hyperthyroid because either she has a mild case of it or because, like we said, she originally was hyperthyroid, but now her thyroid’s burnt-out, and now she’s hypothyroid or she had her thyroid removed before pregnancy or something, but we think the baby’s hyperthyroid, so these antibodies from Graves’ disease are now affecting the baby, what do we do?

Dr. Do: Sometimes we actually give her those antithyroid medications in order for them to cross the placenta and treat baby. And so, we’re treating the baby through treating mom.

Dr. Fox: Yeah. This is one of the times when we talk about, like, fetal treatment or fetal therapy where it actually is…it’s unusual that it’s medication-wise. There are some, but this is one of them where you give mother antithyroid medicine even though she doesn’t need them. So, you’re essentially taking…like we had this situation before where her thyroid is fast and the baby’s thyroid is normal.

Now, we have mother’s thyroid is normal and baby’s thyroid is fast. So, if you give the medication, the baby’s thyroid will come down to normal, but now mom’s thyroid will get low. But that’s not as big a deal for us because we can give her more thyroid. You can’t give the baby more thyroid, you can give the mother more thyroid. And that is one of the other, really…I mean, on our end, it’s pretty cool that you can do that.

But it’s also very fascinating because you have, like, medications affect both, and some cross, and some don’t. But it is treatable if the baby has hyperthyroid, you can give medication. There’s also a way to directly test the baby for thyroid. You can do fetal blood sampling. That’s very rare to do nowadays because you can assess these things sort of through surrogate markers like ultrasound findings, like you said, the heart rate. Interesting stuff. Fascinating.

Now, what do we do for someone, they have hyperthyroid, we are giving them whatever medication we think is necessary again to keep them from not getting thyroid storm, but not so much that we’re gonna harm the baby in any sense? What else do we do in a pregnancy to follow the mother and baby?

Dr. Do: We’re monitoring them closely. So, we’re monitoring their hormone levels of the thyroid, we’re monitoring their antibody levels often because higher levels of antibody correlate with worse risks of getting hyperthyroid for the baby, and we’re then monitoring how baby’s doing in terms of ultrasound markers and fetal surveillance. So, doing growth scans to make sure baby’s not getting too small, doing what we call antenatal testing, or monitoring baby’s well-being with things like biophysical profiles in the third trimester.

Dr. Fox: Yeah. I mean, we follow them similar to like we would someone with hypertension or diabetes or twins, you know, other sort of at-risk or higher-risk pregnancies or high-risk pregnancies because there’s definitely a risk. But if they’re well controlled, if their thyroid is sort of normal or slightly elevated, like we said, and the baby’s not hyperthyroid, it tends to go well, things tend to go fine. And then we make a decision as sort of when to deliver them.

Usually, we don’t let them go past their due date. I guess it depends on the circumstances of the…you know, how bad their thyroid condition is for hyperthyroid. Okay, so that’s hyperthyroid. So, just as a review for hypo and hyperthyroid, they’re different in that one is the thyroid is too slow and the other, the thyroid is too fast. And what confuses people often is the TSH levels, which we monitor, is the opposite.

If your thyroid is too slow, your TSH is high. And if your thyroid is too fast, your TSH is low. So, that’s confusion level number one. Confusion level number two is that they sound alike. And number three is that for hypothyroid, it doesn’t make a big difference if you’re overtreating a little bit, meaning we were talking a lot last week, do they need treatment, do they not need treatment?

And a lot of them probably don’t, but if you do, it’s probably not such a big deal. Whereas hyperthyroid, it’s really the opposite. And you really don’t wanna treat unless you have to. And the other big one is that hypothyroid, the antibodies do not directly affect the baby, the baby’s not really at risk for thyroid issues. But hyperthyroid, with the antibodies, the baby is. Sam, did I miss anything? You’re the expert now.

Dr. Do: You’ve covered it. You’ve got it, baby.

Dr. Fox: Awesome. All right. Thanks for listening, everyone. Hypo, hyperthyroid, we covered it. Thank you, Samantha, for coming in and rocking it with hyperthyroid.

Dr. Do: Great topic.

Dr. Fox: Thank you for listening to the “Healthful Woman Podcast.” To learn more about our podcast, please visit our website at www.healthfulwoman.com. That’s H-E-A-L-T-H-F-U-L-W-O-M-A-N.com. If you have any questions about this podcast or any other topic you would like us to address, please feel free to email us at hw@healthfulwoman.com. Have a great day.

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