sMater | Dr Jo Laurie | Thyroid Disease in Pregnancy

In this episode of sMater,  Mater Obstetric Medicine Specialist Dr Jo Laurie explains the impact of thyroid disease on mother and baby during pregnancy.

Jo is Director of Obstetric Medicine at Mater Mothers' Hospital and offers practical advice for GPs on managing thyroid conditions in pregnant women' through GP Shared Maternity Care.

A detailed guideline on thyroid management in pregnancy with referral pathways can be found at Mater Online.

GP Education activity log:
  Podcast title - sMater: Thyroid disease in pregnancy
  Provider - Mater Misericordiae Ltd
  Date published - August 17, 2024
  Certificate of completion - click here

To learn more about Mater, visit https://www.mater.org.au/

Transcript

Hello and welcome to this episode of sMater. A podcast by clinicians for clinicians brought to you by Mater, an Australian leader in healthcare for more than a century. My name is Jillian Whiting and we're coming to you from Meanjin the land on which this podcast is being recorded. Hello I'm Maggie Robin, Community GP rural GP obstetrician at Beaudesert Hospital and coordinator of Mater's GP shared care education program.

In this episode we're talking about thyroid disease and pregnancy with Doctor 
Jo Laurie. Jo is the director of obstetric medicine at Mater Mothers' hospital and has practiced as an obstetric physician for the last 18 years.

Jo is also a researcher in the impact of maternal illness and pregnancy and the 
longer term. She's joining us to talk about how thyroid disease is treated before, during and after pregnancy.

We are Mater, We are Mater, We are Mater, This is sMater.

Jo, welcome to sMater. Thank you for having me. Firstly how common is thyroid disease in pregnancy?

So it's one of the more common medical conditions but probably only about 1 to 2% of pregnant women will suffer from thyroid disease. So it's something that we're looking out for but you won't see super commonly in general practice. Can you explain the difference between hyper and hypo just briefly? Sure. So hyperthyroidism is when there's an excess of thyroid hormone produced by the thyroid gland. In pregnancy that can be due to just the changing in the hormones the Beta HCG being elevated and that's called gestational thyrotoxicosis or gestational hyperthyroidism and that's a transing condition and then the other sort of hyperthyroidism is generally Graves disease which is an autoimmune condition. Hypothyroidism is an underactive gland where there's not enough thyroid hormone produced and the commonest cause of that is Hashimotos thyroiditis which is the name of the condition and that is relatively common in women of childbearing age. So Jo we know thyroid disease can cause problems for both mum and baby. If we focus first on hyperthyroidism what is the cause or what are the indicators and what are the concerns for mum and for baby.

So if we're talking about Graves disease or autoimmunity that pre-existed the pregnancy it can impact the chances of the woman falling pregnant and then keeping that pregnancy in the first trimester so can increase the risk of miscarriage if it's poorly controlled but like all conditions in pregnancy if we can modify the underlying disease treat it well with medications the risks of adversity related to the condition is reduced and that woman could have a very normal pregnancy.

The signs and symptoms of hyperthyroidism are consistent with that in just the adult population so women are usually hot, they might be losing weight, they might be quite sweaty, they might be tremulous with a tachycardia and with Graves disease specifically they can have Graves eye disease where they have a pyroptotic eye, or a very bright you can see white above the iris when you're looking at the patient it's quite an obvious condition.

So if it's pre-existing to pregnancy you try to settle i down for the pregnancy and then in the early pregnancy try to keep the thyroid hormone levels stable so that they can progress through a fairly normal pregnancy. It can have fetal impacts if even when the disease is well controlled due to the autoimmunity because that crosses the placenta to the baby and so that's something that we tend to look after in hospital, be cognizant of and do some screening and surveillance of that baby.

How much can be treated by a GP and when do they need Specialist Care? So hypothyroidism is actually very easily treated in general practice and we would prefer that be the case because you see them either pre- pregnancy or very early in the pregnancy. So all that entails is that you know how much thyroxin they're on, you increase it automatically by 30%. Don't wait for the blood test just pop the thyroxin dose up by 30% and then retest the TFTs in about 4 to 6 weeks after that to check for compliance and appropriate reduction in the TSH. If you're having difficulty with that very happy to see the patient but probably more easily we could just take a phone call and give some advice over the phone. There's a couple of traps for players in the replacement for thyroxin. The things that we tend to check with patients are that they're taking their medication number one that they're taking it first thing in the morning without any other vitamin so making sure they're not taking it with iron or calcium which can bind it and prevent its absorption. That they don't leave the tablets on the windowsill because if they get hot, particularly in Brisbane, they go off and that their scripts are in date and you know the medication is actually good medication. So we go through that with them as well and if it's still not able to get their numbers in the right profile then we're very happy to see the patient to work with them on that.

And Jo, if you're asking someone to increase the dose by a third how would you advise them to do that?

Yeah so thyroxine is one of the really funny medications where you actually could take the whole week's worth just at once but what we tend to do is we work out how many micrograms they have across the week and work out what a third of that is and that's how you increase. So maybe you're on 75 micrograms every day 7 days a week then you'd go up by 30% would be having two tablets on Saturday and Sunday . So 75 Monday to Friday 150 Saturday and Sunday and that's easier for the patient to take we don't want them breaking tablets and because the absorption is across the week it doesn't actually matter from the tablet point of view.

Jo can you explain for us what is gestational thyrotoxicosis and how do we work out if someone has gestational thyrotoxicosis or a different underlying thyroid problem? So that can be a bit challenging. So I guess the first thing that you look at is the TSH and you'll note that the TSH is suppressed in women who have hyperactive thyroid so then you go on to the next step of what is the 3T4 and 3T3. In gestational thyrotoxicosis it's only usually marginally elevated so you might have a T4 of around 25 and a T3 of around 5. Graves is usually a little bit more severe so that could be 30 or 40 for T4 but the important thing is the antibody levels so you want to test antibodies to check whether they have underlying Graves disease and that is a TSH receptor antibody or a TRAb and if the TRAb is elevated it's extremely likely they have Graves and they need referral urgently into the hospital for us to monitor their baby and work out what surveillance strategy we will use for that woman. With Hypothyroidism Hashimoto's we are very interested in the anti-tpo antibodies specifically so not the anti-tg but the anti-tpo and if there elevated that's when you use your diagnostic pathway that's in the policy to know whether they need treatment to a TSH below 2.5 or whether they can have a treatment just to a TSH below 4.

What's the difference between the thyroglobulin antibody and the TPO antibody?

So TPO is much more impressive for autoimmunity and has more impact on pregnancy outcome whereas thyroglobulin just says that there's a little bit of inflammation in the thyroid gland and it's not useful at all helping us to determine what the risk is for that pregnancy.  Jo, what difference does it make if a woman with Graves disease already has it under control when she falls pregnant and how can you tell that it's not Graves when they've got a really low or undetectable TSH level? So it's very hard with a person who's got known Graves to know whether their undetectable TSH level is important or not. We tend to look at the 34 and 33 there to know what the hormone levels look like to determine whether they need treatment again that's you know something that Specialists do day to day. So very happy to see those patients in hospital.

The tricky part with Graves is women who have had a definitive therapy so they might have had their thyroid gland removed or they might have had radioactive iodine to treat their thyroid gland so their thyroid function is actually normal or they might even be on thyroxine but their risk of neonatal Graves disease so the baby or the fetal Graves disease the baby getting issues with hyperactive thyroid still exists because the autoimmunity hasn't gone away so we still check their TRAbs even though they might not have had their disease for a long time and if their TRABs are positive we do have increased fetal surveillance and neonatal surveillance for that complication those antibodies are very good at crossing the placenta and they can live in the woman for 20 or 30 years after their incident Graves episode.

Women who have had a thyroidectomy and radioactive iodine treatment are recommended to wait 6 to 12 months before becoming pregnant to avoid side effects of radiation being transferred to the baby. Studies have shown that there is an increase in birth defects when pregnancy occurs within 6 months of treatment.

What does the fetal or neonatal surveillance look like? Yes so we tend to look at their heart rate to make sure that the baby's not Tachycardic. We do additional ultrasound scanning to look for a goiter in the baby and to look for evidence again of Tachycardia or even heart failure in the baby. Throughout the pregnancy those babies have a cord blood to look for their thyroid function at birth and also another thyroid function test at about day 5 and we'll check their antibodies as well.

It's a transient condition in the baby but we obviously don't want them to become unwell 

with hyperthyroidism in those very early days.

Jo, during pregnancy how safe is medication and should they stop as soon as they know they're pregnant? So thyroxine is extremely safe so there's no reason to stop that and we talked about the 30% increment with regards to Anti thyroidal treatment they definitely shouldn't stop their medication but their medication does need to be reviewed and we would help do that either by phone call if we can't get them in urgently or you know we can usually see them within a week or two. Our preferred antithyroid medication in the first trimester is PTU because we know that it definitely doesn't have any association with embryogenesis issues. There's very weak evidence that carbimazole might cause some issues with baby's development however in the second trimester and in the third trimester there's an increased risk of liver failure with PTU so we swap them back. So they might have been on carbimazole before the pregnancy and we put them on PTU in first trimester and swap them back to carbimazole in second and third or maybe they're on PTU before and continue that through the first trimester swap them to carbimazole in the second and third because pregnancy improves your autoimmunity so if you've got autoimmune disease it usually gets better in the pregnancy. Often these women can come off treatment in the second and third trimester anyway and we are very happy to manage that.

What about postpartum? The mum's thyroid function is likely to rebound and become hyper thyroid. 

What is the danger period and what should GPs be looking for? So we hopefully have identified them as being at risk of that and organized for them to have an appointment with their endocrinologist or endocrine service at about the 6 to 8 week mark because that's when it happens so they're usually fine for the first 6 weeks postpartum and then if they're going to have a flare of disease and this is any autoimmune disease that'll occur between 6 and 8 weeks. If for some reason they have been missed for their follow up that is the time to do a thyroid function test and refer them urgently if it's abnormal because they're probably not on medication by that stage so they might need to be reminded to bring that under control. Thyroxin we talked about increasing it by 30% in the pregnancy, you need to reduce to pre-pregnancy doses at the end of the pregnancy and check their thyroid function for stability again 4 to 6 weeks afterwards.

Jo, in the past there's been a debate about subclinical hypothyroidism. What can you tell us, what is the latest research on that?

Yes so people get very concerned that their baby's IQ might be less if their thyroid is not perfect during the first trimester and I think there was a very large Scandinavian study which showed that if you are significantly abnormal in your thyroid function that maybe those babies had a slight reduction of one to two IQ points, however we're not talking about this very mild degree of subclinical hypothyroidism so we need to reassure women that their babies will be fine that we will treat to the parameters that are in that pathway. So if their TSH is 4 or below and they're antibody negative that's normal. If they're antibody positive that's antibody TPO then it's down to 2.5 as the treatment Target for TSH we use that as the parameter to treat them. If they're 2.6 or 2.7 it's not going to make a massive difference to that baby at all and we need to reassure women that they're doing very well and that where you know we're working with them to make sure that we're optimizing their pregnancy.

Is there a clear way to communicate that with women? I think just to reassure them that this is a very minor very very slight blood test abnormality and it doesn't have massive clinical consequences. It's important to get that message across.

Research shows that the consequences of maternal hyperthyroidism on babies are the result of various factors acting in combination. While women shouldn't be concerned about neuropsychological effects, it's also important that for their general health and the health of their baby during pregnancy they ensure their thyroid function is within safe parameters.

Jo, do all women need thyroid function testing as part of their routine antenatal blood tests? The short answer is no that's not what the you know College of ONG suggests. It's not what the Australian Endocrine Association suggests however if you're concerned about a woman if she has risk factors any family history of thyroid disease you know it is worth checking and it might reassure you both that that's not part of the concern for that woman. Fatigue as a feature of hypothyroidism is really tricky because everybody's tired so that wouldn't be an indicator but you know I don't think there's any harm in testing but we don't need to get everybody to do it. How much support is there for GPs who need to know the pathway for thyroid disease and pregnancy? So would call their attention to the pathway that's in our policy which gives you a tree to decision tree to follow. Depending on what the blood test look like and what the woman's risk factors otherwise are and I think if you can go there first and work out where she might sit in that pathway that's a really good first step however the obstetric medicine service at Mater Mothers' is available 24 hours a day 7 days a week and we're always happy to take phone calls with questions from GPs about anything including thyroid disease so if you feel that you aren't certain of what the woman needs based on the pathway or she has a slightly more complex history perhaps she's had thyroid cancer in the past please just give us a ring and let us know when we should be able to answer most questions over the phone or at least arrange an urgent follow up for that woman.

A detailed guideline on thyroid management in pregnancy with referral pathways can be found on Mater's website. A link to this guide can be found in the show notes.

Thanks so much Jo. But before we let you go we want to introduce you to our little segment called The Checkup so we want to know more about Jo the person, the medical professional, so we're going to ask you 5 quick questions or Maggie's going to ask you 5 quick questions. You ready? Yes terrified, interested.

Jo, what was your first concert? Probably The Corrs.Who is the most underrated member of the hospital team?

We have high-risk midwives that look after our patients. They're called the OMGP - the Obstetric Midwifery Group Practice and they are amazing and I don't think they receive the amazing accolades that they should.

Yes I've worked with them as well and they work very hard. Yes, yes. If a genie could grant you one wish what would it be? More time in the day. That'd be nice, yes. I think that would be it. And along those lines if you had a day off today what would you do? I would take my dogs for a walk because that's one of my favorite things to do and then sit in sun.

If you weren't doing this job, what would you be doing? I would be a florist. No I've actually always wanted to be a doctor and I'm very pleased that I chose that pathway and I still love what I do every day.

Flowers could be a hobby Jo. Yeah I mean I grow them successfully sometimes and not others but  I just think flowers are beautiful I think nature as well. Well we're glad you're doing what you're doing. Thank you so much for joining us today. Thank you for our listeners at home or in the car or having a well deserved break between patients. Thank you for tuning in. See you next time on sMater.