Hyperthyroidism: Antithyroid Medication (Nursing)

00:01 Let's discuss thyroid pathophysiology and the mechanism of action of antithyroid medications.

00:07 Now there are several use cases I want to talk about.

00:10 First of all, this is a first line treatment for Graves disease.

00:14 Remember that's the most common cause of hyperthyroidism, but you can use it in some other clinical cases.

00:20 We give antithyroid medications in preparation for thyroid surgery.

00:25 It can also be used for treatment during pregnancy when it's necessary.

00:29 It can also be a bridge therapy before radioactive iodine treatment, and we can use it to manage a thyroid storm.

00:37 Antithyroid drugs like methimazole and propylthiouracil, which from here on out I will call as PTU .

00:45 These are medications used to treat hyperthyroidism, which is an overactive thyroid.

00:50 Now they work through a series of steps to reduce thyroid hormone production.

00:54 So these are the two meds MMI and PTU.

00:58 We're going to talk about how they work in the body.

01:00 Because remember our main treatment goal is that we want to reduce the amount of T3 and T4. Those are the main thyroid hormones, so we want less of those hormones to be produced so we can improve the symptoms of hyperthyroidism. Let's take a closer look at the role of each of those players. First, the meds will target an enzyme called thyroid peroxidase. Now this enzyme is crucial for thyroid hormone synthesis.

01:27 And by inhibiting it, these drugs begin to slow down hormone production. Now, when thyroid peroxidase is blocked, iodine can't be properly incorporated into the thyroglobulin.

01:39 Remember that's a protein in the thyroid gland.

01:41 So iodine is essential for making thyroid hormones.

01:45 So if you block this step this further reduces hormone production.

01:50 Antithyroid medications also prevent the coupling of iodine tyrosine molecules. So think of it like preventing two puzzle pieces from connecting Iodot yrosines need to join together to form active thyroid hormones and these medications prevent that connection.

02:07 Iodot yrosines are created when an iodine item attaches to tyrosine. Remember that's an amino acid.

02:14 So this happens within the thyroglobulin of the thyroid gland.

02:18 Now there's two main types.

02:19 Look at the difference there.

02:21 You've got MIT and DIT.

02:25 Now for the monoiodotyrosine ( MIT).

02:28 It has one iodine atom attached to the tyrosine.

02:32 That's where you see the word mono at the beginning.

02:35 So it has one iodine atom.

02:37 It's the first step in the process.

02:39 And it's created when thyroid peroxidase adds one iodine to tyrosine.

02:44 Now DIT has two iodine atoms attached to the tyrosine.

02:48 It's the second step in the process.

02:50 And it's created when a second iodine is added to MIT.

02:55 Let me break down the coupling process a little closer.

02:58 So in the coupling process two DIT molecules join and they form T4 thyroxine, one DIT and one MIT join to form T3. Now this coupling process is also catalyzed by thyroid peroxidase. So now you can see why blocking the coupling of iodo tyrosines effectively reduces thyroid hormone production.

03:21 It's because it prevents these building blocks from joining together to form the final active hormones.

03:26 And that is how antithyroid drugs work.

03:29 Now, it's also worth noting that the thyroid has a recycling system for any unused iodo tyrosines. They're broken down and the iodine is recovered for reuse, which helps conserve this valuable mineral.

03:41 Now, we've looked and talked about how the drugs prevent the coupling process.

03:44 Now let's talk about the end result.

03:47 Again, that end result of these antithyroid medication is a decreased production of T3 and T4, which are the main thyroid hormones.

03:56 And when there's less of these hormones then the symptoms of hyperthyroidism improve.

04:01 So that's the mechanism of action of antithyroid medications in a nutshell.

04:07 Let's look at these specific and unique assessments you need to complete for any client receiving antithyroid medications.

04:14 Now I want to start with unique populations first.

04:17 Let's talk about pediatrics.

04:19 So when pediatric patients are receiving antithyroid medications there's usually a preference to give them methimazole.

04:25 And that's because it has a lower risk of liver toxicity.

04:29 Now you're going to have to do careful dose adjustment based on the pediatric patients weight. Finally this is very important.

04:36 You need to closely monitor growth and development for your pediatric patient receiving any of these antithyroid medications.

04:44 Now, for the older adult, they potentially could have compromised organ function. So you want to make sure that their doses probably will start with a lower dose.

04:52 You're going to monitor their cardiovascular effects.

04:55 And remember all older adult patients have a higher risk of drug interactions. Now, what about pregnant patients? Well, P2 is preferred in the first trimester.

05:05 And then you'll switch to Methimazole after the first trimester.

05:08 Now they're going to need regular monitoring of thyroid function that's essential throughout their pregnancy.

05:14 Now let's look at the baseline test for everyone.

05:16 You're going to do a CBC liver function test and thyroid function tests.

05:21 And I've listed them for you TSH, free T4 and free T3. Now every client will need regular monitoring.

05:30 In the beginning, it needs to be every 2 to 4 weeks until they're stabilized.

05:34 Then every 2 to 3 months is fine.

05:36 Now you're going to need to do immediate testing if the symptoms of agranulocytosis develop. So be sure to educate your patient about what those symptoms are.

05:45 And there you have the key assessments for any client receiving antithyroid medication.

05:52 Most drugs have some type of adverse effect.

05:55 Antithyroid, medications are no exception.

05:58 So we're going to talk about adverse effects and the black box warnings for antithyroid medications. Now the most common adverse effects include things like rash, arthralgias, GI upset, some minor liver function abnormalities might also occur, but black box warnings are a different story.

06:18 Antithyroid medications have a risk of agranulocytosis, so you need to be aware to assess for this and to teach your patients the signs and symptoms to look for. You also have a risk of severe liver injury, particularly with PTU.

06:32 Now both of these conditions will require immediate discontinuation of the medications. So we've talked about the common adverse effects.

06:41 We've talked about the black box warnings which are going to think of agranulocytosis and liver injury. Those are the key things that you'll need to watch for and educate your patients about who are receiving antithyroid medications.

06:54 educate your patients about who are receiving antithyroid medications.

06:55 Every member of the healthcare team has a role to play in patient education and or caregiver education, as appropriate.

07:02 So for your patients on antithyroid medications, these are the things you want to keep in mind.

07:08 If they tell you that they have GI upset with the medications, tell them they can take the medication with food.

07:14 Now, it's important they understand the value of consistent timing of doses.

07:18 Their doses will usually be divided into 2 or 3 different doses.

07:23 Remind them do not crush or split unless that's specifically approved by the healthcare provider.

07:29 Make sure they report any fever, sore throat, or unusual bleeding. Remember, this is a risk of agranulocytosis developing. They have to have their regular blood tests done when you've required them to have them.

07:43 So make sure they understand that this isn't a minor thing.

07:46 It's critically important to their safety that they have their blood tests done regularly. Now, if they're on the medication, it's usually best if they can avoid pregnancy, but that is a much more complicated discussion.

07:57 Also, remind them to report any yellowing of the skin and eyes immediately, as that indicates a problem with their liver.

08:04 Now, these medications are powerful.

08:07 Some primary care providers recommend care under the supervision of an endocrinologist, and collaborative care is always the best.

08:14 Also, last piece remind your clients that consistent and good hydration is also important to their health.