2 Thyroid - Final Edit
[00:00:00] Okay. Welcome back to Behind the Knife's Ab Site Review. The topic today is thyroid. So again, high yield anatomy. So Kevin, I'm going to go to you for all the vascular questions. So what's the vascular supply to the thyroid? Walk me through it. Okay. So let's start with the superior thyroid artery, which is, you know, commonly pimped vascular question is the first branch of the external carotid artery.
And then you have your inferior thyroid artery, which is a branch of the thyrocervical trunk. And then you have your thyroid IMA artery. It's an anomalous branch, usually from the nominate artery directly to the isthmus. And then, of course, you have to have veins. So you have your superior thyroid vein, the strains directly into the internal jugular vein.
And then you have your inferior thyroid vein, which drains into the innominate vein. Great. And again, we have an image that goes along with that. So just review the companion and make sure you understand that vascular anatomy. Moving on to nerves, John. So, you know, I think the two most pertinent nerves are [00:01:00] when it, when it comes to specifically head and neck and especially thyroid is the superior laryngeal nerve and the recurrent laryngeal nerve.
So superior laryngeal nerve, what does it innervates and what happens if it were to get damaged? Yeah, the superior laryngeal nerve is the motor to the cricothyroid muscle. And injury to this, you would lose projection and fatigue during speaking. For the recurrent laryngeal nerve remember the right travels with the vagus and loops around the anomen artery, and the left originates from the vagus nerve near the aortic arch looping around the aorta.
The injury to the recurrent laryngeal nerve is that you can get paralysis of the vocal cords. If you get injury bilaterally, it can obstruct the airway. Yeah, so that's, you may want to consider preoperative laryngoscopy to visualize the cords especially at, at higher risk patients. So moving on from anatomy, let's talk a little bit about physiology.
So thyroglobulin and calcitonin are, are really two of the important proteins to understand. So what's the function, Kevin? of [00:02:00] thyroglobulin and calcitonin. So thyroglobulin comes from follicular cells, and this facilitates synthesis of T3, the more active form, and T4. Calcitonin comes from C cells.
And this actually lowers the serum calcium via multiple mechanisms. Yeah. So this is, you know, as with all endocrine organs, it's important to understand the function because a lot of times the question on the test is going to be related to the endocrine function of these organs as well as the pathology.
So there's not a lot to talk about embryologically that I think is super high yield for the outside. One thing, though, is talking about fibroglossal duct cyst, which is resultant from the pyramidal lobe extension. The thing to remember is that it has malignant potential. So it's important, important to, to resect this if.
If you do have a thyroglossal duct cyst otherwise let's move on to a little bit of that pathophysiology. So let's talk about hyperthyroidism. So John, what lab findings are [00:03:00] found in hyperthyroidism? Yeah. So for the test, if you were in clinically, if you had a patient with suspicion of hyperthyroidism, you'd order a, you'd order a thyroglobulin tests as well as a TSH.
You would find on your results, low TSH and elevated T3. Okay. All right. And what are some of the common medications that are used to medically treat hyperthyroidism? So a few options are PTU. It's the side effects of this are aplastic anemia and agranulocytosis. However, PTU is if you see the option of a pregnant patient is safe to be used during first trimester pregnancy.
as it does not cross the placenta. Another option is methamizole. And the side effects with this drug are creatinism, aplastic anemia, and also agranulocytosis. Okay, great. So, yeah, PTU and methamizole. So... The thing that comes up is that pregnancy question. So both can are, [00:04:00] can actually be used in pregnancy, but during the first trimester you want a PTU as it does not cross the placenta.
And then later in the pregnancy typically transocean over to methamizole. Okay. Kevin, so let's talk a little bit about Graves disease. So how's Graves disease diagnosed? So there's two ways to diagnose Graves disease. You can give them the radioactive iodine and you'll see diffuse uptake. Or you can also test for the antibodies against TSH receptors.
Okay. What about management of Graves disease? So, you can use your antithyroid medications. You can use radio ablative therapies, radio iodine ablative therapies, or you can resect it with a thyroidectomy. Okay. So what's, when you're approaching a resection what are some important principles? So you want to make sure they're in a euthyroid state prior to the surgery to avoid a thyroid storm.
Okay. How about is there any, what's a Lugol solution? I've heard about Lugol solution when it comes to thyroid storm. [00:05:00] Yeah, I've never really used it, but apparently it decreases the thyroid vascularity and makes it firmer and easier to resect. Okay. Let's talk a little bit about that, John, about then multi nodular goiters.
What are some clinical manifestations of multi nodular goiter and how are these approached and treated? Yeah, you might see a question explaining a multi nodular goiter and that you'll see radio iodine uptake in multiple locations within the thyroid gland. And then surrounded by suppressed thyroid gland tissue, the management for this you can use medications, but the traditional managers, total or subtotal thyroidectomy.
Okay. So I want to go back a second and talk a little bit more about thyroid storm. So Kevin, you mentioned it, so what are the signs and symptoms of a thyroid storm? And how do you treat? Yeah, so these patients will generally they can have a lot of different manifestations and it can be life threatening.
So sometimes they present with hyperthermia, they can have CNS manifestations, cardiovascular [00:06:00] dysfunction. And then to treat them, you generally do supportive care, including cooling blankets, radioiodine ablative therapies, and thyroidectomy. Okay. So, you know, another common cause of hyperthyroidism and ultimately even progressing to hypothyroidism is, is, is thyroiditis.
So John, what's the, when we talk about thyroiditis, what's the most common causes of thyroiditis and how do we manage and approach these? Yeah, the, there's three main types. The one you get a lot more questions on is Hashimoto's and this is caused by antithyroid peroxidase or anti TPO antibodies. And it presents with a painless goiter.
Management is thyroid hormone replacement. The second one is subacute granulomatous. It's painful maybe related to viral infection. You'll see low uptake on your radioiodine uptake scans. And the management for this are NSAIDs and steroids. And the third one is Riedel thyroiditis. It's chronic inflammation [00:07:00] causing fibrosis.
Present, has a hard, non tender. and is associated with hyperthyroidism. The management for this is thyroid hormone replacement and steroids. Yeah, great. So, yeah, just be familiar with those different types of thyroiditis and again, things like the Hashimoto's and its association with the anti TPO antibodies.
As well as some of the different histologic descriptions, because you may see those in written into a question stem and asking you what the treatment would be. Let's move on to thyroid nodules and malignancy. So something that comes up frequently is how the diagnostic evaluation of a thyroid nodule.
So Kevin, where do you start with a thyroid nodule? Yeah. So ultrasound is a really critical part of this. And so you get a good ultrasound and what you're looking for in it is whether it's hypoecogenic, whether it has micro calcifications, irregular margins, unorganized vascular patterns, lymphatic invasion, or if it's taller than wider in the transverse plane.
And then [00:08:00] with, after this ultrasound, you're generally going to get an FNA. Okay. And so something that's important when it comes to evaluating that FNA is the Bethesda criteria. So this is, we have a table in the book that I would refer to and make sure you're familiar with these because these very commonly show up.
So, we'll, we'll break it down. So Bethesda criteria one is indeterminate. And what you do with that is you repeat the FNA. Number two, benign repeat ultrasound and six to 12 months number three atypical atypia of undetermined significance or follicular lesion of undetermined significance.
This is honestly is the one I see most often on the test. They'll come up with the Bethesda three. It'll ask you what to do. And the answer is repeat FNA. For Bethesda Criteria 4, that's a follicular neoplasm, it's a lobectomy. For 5, it's a suspicious malignancy, also a lobectomy. And then Type 6 is malignancy with a total thyroidectomy being the recommendation.
John, how about [00:09:00] thyroid lymphoma? How do we diagnose thyroid lymphoma and how do we treat it? Yeah, like most thyroid diseases, we diagnose it with an FNA, which will show large, irregular lymphoid cells. It has an excellent response to chemotherapy alone. Some of the drugs you would use for that are R chop, rituximab, cyclophosphamide, hydroxy, Rubicon, and Oncovin, which is also known as Vincristine.
And finally, prednisone. If there are compressive symptoms present in a thyroid lymphoma, you can consider radiation therapy. Excellent. So, thyroid lymphoma, lymphoma chemotherapy with R chop. And then if compressive symptoms add radiation therapy. Okay. How about the, epidemiology and some diagnostic findings in papillary cancer.
Kevin. Yeah. Extremely high yield here. It's the most common thyroid malignancy more commonly seen in female patients and it spreads via lymphatic spread, which is important for you when you have, you know how you do your, you do a lymph node resection in these [00:10:00] patients. If it is advanced because it's spread through lymphatic.
So What is classic on the F and a, you should know what these look like also, not just the name of them, because I have heard and seen of them just posting pictures of these. It's the F and a will show some mobile bodies and the orphan Annie nuclei. So Google image search those and make sure you know what those look like.
Okay. How about there's yeah, totally agree with that. Those are definitely one you should Google image and know what it looks like. Cause that's something that might show up as an image question on the outside. And now how about the, there's something very unique about staging of papillary thyroid cancer.
And what is that, Kevin? Yeah, it's very interesting. It's, it's age based. 55 years old and no distant Mets at stage one, if it's distant Mets. Then it's stage two in a less than 55 year old stage three and four disease can only occur in patients older than 55. Yeah. So age is very important in the staging of papillary thyroid cancer, which is kind of unique.
How do we manage [00:11:00] thyroid cancer, Kevin? So these patients need a thyroidectomy. Now you have the option of a total thyroidectomy versus a lobectomy. A lobectomy is an option if you have less than four centimeter disease without nodal involvement or local invasion. But there are some advantages to the total thyroidectomy.
If you're in between the two, it allows for surveillance based on thyroglobulin levels. And then you can also do postoperative radio iodine treatment. And this can also remove any potential multifocal disease. As far as lymph nodes go, it's a little bit controversial and it's beyond the scope of kind of what you're expected to know.
But if you have a suspicious lymph node in a compartment, you're going to do a lymph node dissection of that compartment. So it's either going to be the central level six lymph node dissection. If you have a suspicious or clinically positive node, you'll do a central neck dissection, or if you have a positive node in the lateral levels two through four, then you'll do a lateral neck dissection.
Great. Yeah. A little bit of nuances there with, with some options for, for papillary thyroid cancer, but [00:12:00] for the outside, it should be pretty clear. They're probably not going to give you anything too controversial or too tricky. So John, for let's go, let's switch now to follicular thyroid cancer. How do you diagnose this and what's your approach?
Yeah, a few things to know about follicular thyroid cancer. It's also more common in women and it has hematogenous spread. The FNA for thi for liquid thyroid cancer is not reliable. So a lot of times you need to do a diagnostic or a therapeutic lo lobectomy. The management for this is total thyroidectomy with a modified radical neck dissection for positive nodes and postoperative radio iodine ablation.
You can consider a thyroid lobectomy if the nodule is less than four centimeters. The patient is less than 45 years old. There's no signs of distant disease, which think about homogenous spread, and there's no personal or family history of thyroid cancer. Great. Okay. So how about moving on now to medullary thyroid cancer?
[00:13:00] So, Kevin, talk to me about medullary thyroid cancer, pathophysiology, management. Yeah, so this one originates from the parafollicular C cells. 20 percent of them are associated with the commonly tested germline mutation in RET oncogene, R E T, RET oncogene. Management of the medullary thyroid cancers is with a total thyroidectomy with a central neck dissection and then a modified radical neck dissection if the lymph nodes are involved.
Yeah. And of course you want to monitor for surveillance after that with checking your CEA and calcitonin levels. Now moving on, you know, we can't finish the discussion about medullary thyroid cancer without talking about the MEN syndromes, which can be very confusing. But what's important to remember is that MEN2A and MEN2B are associated with medullary thyroid cancer.
There, which the, you know, the risk is somewhat individualized based on specific gene mutations but the general [00:14:00] recommendation is for prophylactic thyroidectomy. The timing can be a bit confusing. So John, how do we understand this? Let's break it down into, you know, low, medium risk, high risk, and then, you know, our highest risk.
patients. When should those patients be getting their prophylactic thyroidectomy? Yeah. So once you determine the risk on this for your low risk and medium risk patients, you typically want to do the prophylactic thyroidectomy by five years of age. For the highest risk patients you want to do it within the first year of life.
You can delay the prophylactic thyroidectomy as certain criteria are met. And that is if you have normal annual. Serum calcitonins normal annual neck ultrasound and a family history of a less aggressive medullary thyroid cancer. Okay, perfect. So for our lower risk patients, you know, generally, yeah, by five years is a good idea, but it can be delayed based on those factors.
You know, for a high risk patients, definitely by five years. And then for that highest risk category, it needs to be done as soon as possible within the [00:15:00] first year of life. So unlikely you'll get into that level of detail on the outside. But for most other than the highest risk patients, just remember by five years of age for that, for that prophylactic thyroidectomy.
Okay. So now it's time for our quick hits for today. So, let's do it. So Kevin, what antibodies are associated with Graves disease and Hashimoto's thyroiditis? So for Graves, you have your anti TSH receptor. antibodies. And for Hashimoto's, you have your antithyroid peroxidase. Okay. John, what thyroid malignancy cannot be treated with radioactive iodine?
Yep. It's the only one. It's medullary thyroid cancer. Good. Medullary thyroid cancer does not respond to radioactive iodine. Kevin, where is the recurrent laryngeal nerve most commonly injured? Near the ligament of Barry. John, where is the superior laryngeal nerve most commonly injured? That's near the superior pole of the thyroid and usually during the ligation of the superior thyroid artery.[00:16:00]
Okay, good. What's next? So what's the most common symptom of an elevated calcitonin? Yep, that'd be diarrhea. Yep, pretty non specific, but diarrhea is the most common symptom of an elevated calcitonin. Okay, and finally, what group of nodes are found within the anterior, anterior suspensory ligament? And what is their clinical importance?
It's the Delphian nodes. They're at the level six. And these are the frequent first site of Mets during thyroid cancer. Excellent. All right. That does it for our outside review of the thyroid. Thanks for listening.