Rob Steele, MD (Host): Welcome to Pediatrics in Practice, a CME podcast. I'm your host, Dr. Rob Steele, Executive Vice President and Chief Strategy and Innovation Officer at Children's Mercy, Kansas City. Before we introduce our guest, I wanted to remind you to claim your CME credits after listening to today's episode. You can do so by visiting cmkc.link/cmepodcast and click the Claim CME button.

Today, we are joined by Dr. Jennifer Boyd to discuss congenital hypothyroidism in the primary care setting. Dr. Boyd is a pediatric endocrinologist at Children's Mercy Kansas City and Assistant Professor of Pediatrics at the UMKC School of Medicine. She specializes in helping childhood cancer survivors who are at risk for endocrine disorders and provides care in our Endocrine Disorders in Cancer Survivors Clinic, as well as other Oncology's Survive and Thrive Clinic. Her research focuses on adrenal insufficiency. Dr. Jennifer Boyd, thank you for joining us today.

Jennifer Boyd, DO: Thank you for having me, Rob. I appreciate it.

Host: So, in the notes that came to me beforehand, it looks like you're a pretty active person, golfing and gardening and working out in the gym.

Jennifer Boyd, DO: I try to be. Some months are better than others.

Host: Yeah. I wonder, is that all related to being an endocrinologist and, I don't know, just trying to stay fit? Are they related in any form or fashion?

Jennifer Boyd, DO: I think it definitely gives some motivation to try to be active and, try to stay healthy. I think my initial training was in dance. Actually, my undergraduate degree was in dance. So, I think, partly just movement means my mental health is better and I feel better.

Host: Yeah, I'm the same way, although I do like your combination of golfing and gardening. For me, I would need the gardening to find my zen after just losing it on the golf course. That's for sure.

Jennifer Boyd, DO: So true. That is exactly right.

Host: Well, why don't we jump right into it? Speaking initially of congenital hypothyroidism, can you just explain what is congenital hypothyroidism and maybe who's at most risk?

Jennifer Boyd, DO: Sure, absolutely. So, it's an inborn condition in which the thyroid hormone levels are insufficient for just the normal development and function of the body. And so, it's actually fairly frequent. The incidence is one in 2,000 to one in 4,000 births. So, we do see it fairly frequently. It is one of the most common preventable causes of intellectual disability worldwide. So, it's very important that we identify it. Females are slightly higher risk than male babies. Babies with trisomy 21 or Down syndrome, as well as our premature infants and certain genetic conditions make you more at risk for congenital hypothyroidism. So, those are the ones we may see most often.

Host: Yeah. And I can remember in practice, having practiced in a couple of states, a few states, I imagine the screening for congenital hypothyroidism is pretty standard for the newborn screening. Is that true across all 50 states?

Jennifer Boyd, DO: Yes. So, in the U.S., the newborn screening programs are allocated by state, but every state and most countries worldwide have newborn screening for congenital hypothyroidism in place. But the different states do use different strategies for newborn screen, which I do think is important. In Kansas and Missouri, we use a particular screening mechanism. But in other states, they might use a different mechanism, which is important for the pediatricians to know.

Host: Is it fair to say that there are those with potentially congenital hypothyroidism that might screen normal, but because of, you know, you mentioned trisomy 21 and other possibilities that those drop off later on. Is that a common theme that you see with patients that are referred to you?

Jennifer Boyd, DO: Yes. So, it is something that we may have a newborn screen that is positive, because the TSH is elevated, and we identify them early. But sometimes we will find it a little later and months down the road even. And so, that is certainly something we'll see.

Host: So, what would you recommend with regard to screenings aside from the newborn screening, which happens with each baby? Do you generally start with newborns? Are there other guidelines with which the primary care physician should be thinking about screening?

Jennifer Boyd, DO: Absolutely. So, all newborns should have a newborn screen. It's critical that it's done for identifying hypothyroidism early and in a timely manner. But anytime a child has symptoms of hypothyroidism, we also recommend doing testing for hypothyroidism. So, that involves doing a blood test, what we call a TSH and free T4, doing that blood test. We tell families that, you know, sometimes there's a mix up with the newborn screen in the newborn nursery. And other times a kid may be born with what we call a central hypothyroidism that won't pop up on the newborn screen. So, it is important for pediatricians to keep that in mind and just always screen for hypothyroidism if a child is showing symptoms.

Host: I can remember back when I was in residency just a while ago, I mean, really just-- For those of you listening, my blonde hair is not blonde, it's more gray. But the recommendation for that screening was a free T4 and TSH. Does that remain the general...?

Jennifer Boyd, DO: It does. TSH and free T4 are the mainstays in screening for both the most common type, which is a primary hypothyroidism, meaning a defect in the gland itself as well as central hypothyroidism, which the defect is higher up in the hypothalamus or pituitary. So, a TSH and free T4 will identify if there's a primary or central hypothyroidism present.

Host: Great. That's very helpful. As you may know, we've got a lot of primary care physicians that are listening to this and that's very, very helpful, particularly when they're wondering, "Do you just get the TSH?" And I think it's important to recognize getting both the free T4 and TSH. So, Dr. Boyd, could you give our listeners some of the examples of congenital disorders of the thyroid gland that one might typically see?

Jennifer Boyd, DO: Absolutely. I think to understand the causes and the different causes of congenital hypothyroidism, it is first nice to review how a normal functioning thyroid system behaves or works. So, like most endocrine systems, the thyroid system is a feedback loop. So, meaning that the hormone production and the hormone concentration are maintained by a feedback mechanism. And so, we call that thyroid system the hypothalamic-pituitary-thyroid axis or HPT axis. The hypothalamus makes a hormone called TRH, and this stimulates the pituitary gland to make TSH. And that pituitary TSH stimulates the thyroid gland to make thyroid hormone known as thyroxine or T4. That is what we screen when we do those newborn screens, the TSH and T4. And then, that feedback mechanism comes in when the hypothalamus and pituitary gland sense there's an adequate T4 and T3 around, and thus, lowers the TRH and TSH secretion. And at times, when the hypothalamus and pituitary gland sense there is not enough of that T4, T3 around, they increase TRH and TSH secretion to help bring those thyroid hormones back in balance.

And I like to explain this system to family and I liken it, our HPT access, to our air conditioner units in our house. So, I'll explain to families, our AC system will try and keep our house at a particular temperature. At my house, we argue about what that temperature should be.

Host: Same. Same on mine too. I'm with you.

Jennifer Boyd, DO: But then, the AC unit turns on and off during the day to try and maintain that temperature. And so, that is exactly what our HPT system is trying to do. The different causes of congenital disorders of the thyroid gland can be at any part of that axis. So, we have kids that have a hypothalamus defect or a problem with that malformation or a pituitary gland defect, or the most common is a primary thyroid defect.

The most common causes are a defect in the thyroid gland development, so thyroid dysgenesis or thyroid ectopia or thyroid hypoplasia. There can also rarely be an intrinsic defect in the thyroid hormone synthesis, so a malfunction of one of the enzymes in the gland. And, in those cases, kids oftentimes will have a large thyroid gland, which may make the pediatrician say, "Oh, is something going on here?"

So, less commonly, it can be due to the mom having an antibody or maybe a mom being on a medication that disrupts thyroid function or, in other countries, less often hear iodine deficiency. So, I'd say one of the least common ones is one that's called central hypothyroidism where there's a malformation in the hypothalamus or pituitary, so central hypothyroidism.

Host: Yeah. That's why I love the air conditioning metaphor. That is perfect. I kind of envision that you probably draw this out. You draw the whole axis out. You've gotten really good at drawing your thyroid and your hypothalamus and all that, and your pituitary. That's fantastic. Well, I'm going to use that actually. I really love that air conditioning.

Moving into more management of these patients, those that do have congenital hypothyroidism, do you have any pearls of wisdom on how best to manage those, particularly maybe for the younger patient, talking with the families about how to manage that?

Jennifer Boyd, DO: Well, we are lucky that the medication comes in a tablet form that is not a gross medication to take. So, all babies just tend to be okay with taking it. So, we advise the family that it's best to take the medication called levothyroxine, so a thyroid hormone supplement. And we have them crush the tablet and draw it up with some liquid breast milk or formula and give it to the baby and they usually just kind of take it into their mouth and suck on it and swallow it just like they would any other formula or breast milk that they're taking. We recommend taking it once a day, and it's preferable that it is about the same time every day. Probably one of the most important education we do is telling families not to give it with calcium supplements, multivitamins, soy formula, iron. All of those can decrease the absorption of the medicine. And so, we just counsel them and trying to give it away from those if the baby does need those.

Host: Very good. Yeah, great pearls on that one. You had mentioned at the top of the podcast that either one of the most or the most common causes of intellectual disability is untreated hypothyroidism. I'm going to assume that that doesn't happen too often, at least in the United States. But can you talk a little bit about what happens when we actually treat, and what the outcomes really are when we treat hypothyroidism?

Jennifer Boyd, DO: So, the children that are identified early and that we are able to normalize their thyroid hormone levels in three to four weeks, really have near normal to normal neurocognitive development. It's children that are missed, maybe didn't have a newborn screen, those are children that are at risk for neurocognitive delays. And so, it is so critical to identify children with the newborn screen. I have one study that showed before the newborn screen, 25% of kids with congenital hypothyroidism had intellectual disabilities. Now, with newborn screening, it is less than 1%. So, it has been a very impactful thing that all states have this, and that it's followed.

Host: Great. Dr. Boyd, we really appreciate your expertise, as well as going through the physiology and pathophysiology of congenital hypothyroidism, very helpful, as well as treatment and the positive impact we can have with early treatment. Before we go, I have to ask you, you know, we all have rough days and rough weeks. At the end of a rough week, a challenging week for you, you've already mentioned you like golfing, gardening, working out in the gym, what's your go-to? Where do you release your stress?

Jennifer Boyd, DO: That's a great question. I'm fortunate to have quite a few avenues, but probably getting my two girls, I have a 12-year-old and a six-year-old, outside gardening is one of my favorite things to do. Just being outside with them and just watching the joy of their faces is probably my go-to for stress relief.

Host: That's fantastic. Yeah, I'm an outdoor person myself. And, as my kids say, "You got to get them out and touch some grass." So, that's exactly right. Yeah, well, that's great. Very good. Well, Dr. Jennifer Boyd, thank you again for joining us today. As a reminder, claim your CME credit for listening to our show today. Visit cmkc.link/cmepodcast and click the Claim CME button. This has been another episode of Pediatrics in Practice, a CME podcast. I'm Dr. Rob Steele. See you next time.