22: Thyroid Flashcards

Question

What is the approach to the thyroid in patients with MEN2a and MEN2b?

Answer 1

Prophylactic thyroidectomy and central node dissection: * At **2 years** of age in **MEN2b** * At **6 years** of age in **MEN2a** [UpToDate: In patients with MEN2, there is predictable progression from multicentric hyperplasia of the parafollicular C cells of the thyroid gland to **medullary thyroid cancer** (MTC), with a **penetrance approaching 100%**. MTC in patients with **MEN2B is more aggressive than in MEN2A**, and total thyroidectomy is often not curative. The goal in patients with known **RET mutations** (but without clinically apparent disease) is to perform a prophylactic thyroidectomy before MTC develops or when it is still confined to the thyroid gland. Children with certain RET mutations can develop clinically apparent MTC at an early age. These mutations can be categorized as highest, high, and moderate risk, referring to the potential risk for local and distant metastases at an early age, as follows: Highest risk – For children with a predisposition for **MEN2B**, most commonly associated with a germline mutation in codon 918, we suggest **thyroidectomy during the first year of life** (Grade 2C). High risk – For children with RET mutations in codons 634 or 883, we suggest total **thyroidectomy at or before age five years** (Grade 2C). Moderate risk – For patients with MTC and RET mutations other than M918T, C634, and A883F in codons 609, 611, 618, 620, 630, 666, 768, 790, 804, 891, and 912, we suggest total **thyroidectomy during childhood or young adulthood**, based on detection of an elevated serum calcitonin level (above the upper limit of normal).]

Answer 2

* Thioamides (50% recurrence) * ¹³¹I (5% recurrence) * Thyroidectomy if medical therapy fails (bilateral subtotal 5% recurrence or total thyroidectomy requiring lifetime thyroxine replacement) [It is unusual to have to operate on these patients (suspicious nodules are the most common reason to operate). Indications for surgery include a noncompliant patient, recurrence after medical therapy, young patient, pregnant women not controlled with PTU, or concomitant suspicious thyroid nodule.]

Answer 3

* Thyroiditis caused by a viral upper respiratory tract infection * Treatment is steroids and ASA [May need lobectomy to rule out cancer in patients with unilateral swelling and tenderness. May need total thyroidectomy for persistent inflammation.]

Answer 4

* Papillary thyroid cancer: **Lymphatic** spread, metastasizes to the **lung** (rare) * Follicular thyroid cancer: **Hematogenous** spread (50% have metastatic disease at time of presentation), metastasizes to the **bone** * Medullary thyroid cancer: **Lymphatic** spread (most have involved nodes at time of diagnosis), metastasizes early to the **lung, bone, and liver** [Hurthle cell carcinoma metastasizes to the **bone** and **lung** if malignant.]

Answer 5

Midportion or all of the hyoid bone [Thyroglossal duct cysts should be resected because they are susceptible to infection and may be premalignant.]

Answer 6

* Provides motor innervation to what? **All of the larynx except the cricothyroid muscle** * Runs where in relation to the thyroid lobes? **Posterior** to thyroid lobes in the **tracheoesophageal groove** * Tracks close to which artery? **Inferior thyroid artery** (variable) * Injury results in what? **Hoarseness**, **bilateral injury can result in airway obstruction** requiring emergency tracheostomy [UpToDate: A **non-recurrent RLN** may be present in nearly **1% of patients**. When present, the nerve will course directly from the vagus nerve to the trachea. Rarely, the right inferior laryngeal nerve may not recur and instead crosses transversely from the vagus nerve and behind the common carotid artery; in almost all instances, it enters the larynx at the usual level. Non-recurrence of the inferior laryngeal nerve results from a vascular anomaly during embryonic development of the aortic arches in which the fourth vascular arch and right dorsal aorta involute, causing the aberrant development of arterial structures on the right, including the lack of an innominate artery and the passage of the subclavian artery behind the esophagus. A non-recurrent left inferior laryngeal nerve would require a right aortic arch associated with situs inversus and is exceedingly rare.]

Answer 7

Substernal goiter [UpToDate: The most common symptom in patients with obstructive cervical or substernal goiter is exertional dyspnea, which is present in 30% to 60% of cases. This symptom usually occurs when the tracheal diameter is under 8 mm. Bilateral thyroid lobe enlargement, especially if the goiter extends posterior to the trachea, may cause either compression or concentric narrowing of the trachea or compression of the esophagus or jugular veins. With some goiters, there is growth of one or both lobes through the thoracic inlet into the thoracic cavity, which can result in obstruction of any of the structures in the inlet. Such goiters are referred to as substernal (image 1A-B). Patients with obstructive symptoms from a cervical or substernal goiter require removal or ablation of the thyroid. For patients with obstructive goiter, we suggest surgery rather than radioiodine (Grade 2C). The reduction in thyroid volume with radioiodine is only moderate, and there are theoretical concerns that radioiodine could acutely worsen obstruction or a missed malignancy. However, radioiodine therapy is an option for patients with obstructive symptoms who are poor surgical candidates. For asymptomatic patients with normal flow-volume loops whose goiters end at the level of the brachiocephalic vein or higher, we suggest observation rather than surgery (Grade 2C). We monitor such patients with serial computed tomography (CT) scans, initially after one year, and if stable, at increasing intervals (eg, two years later, then three years, then five years). Recommendations for asymptomatic patients with goiters that extend below the level of the brachiocephalic vein are controversial. The author of this topic suggests surgical excision for most patients except older patients and those who are poor operative candidates, while other experts suggest observation of asymptomatic patients. All patients requiring surgery for substernal goiter should be referred to experienced thyroid surgeons in high-volume centers to minimize complication rates. For most patients undergoing surgery, we suggest a total or near-total thyroidectomy rather than subtotal thyroidectomy, to minimize the risk of recurrent goiter (Grade 2C).]

Answer 8

* Staph or strep upper respiratory tract infection * Treatment is with antibiotics [May need lobectomy to rule out cancer in patients with unilateral swelling and tenderness. May need total thyroidectomy for persistent inflammation.]

Answer 9

* Preoperative PTU should be administered until euthyroid * Beta-blockers * Lugol's solution for 14 days to decrease friability and vascularity (start only after euthyroid)

Answer 10

* The Tubercle of Zuckerkandl is the most lateral, posterior extension of thyroid tissue * Left behind with subtotal thyroidectomy because of the **proximity to the recurrent laryngeal nerve** (Rotate it medially to find the recurrent laryngeal nerve)

Answer 11

Fine needle aspiration is the best initial test [90% of thyroid nodules are benign. There is a female predominance.] [UpToDate: The initial evaluation in all patients with a thyroid nodule (discovered either by palpation or incidentally noted on a radiologic procedure, such as carotid ultrasonography, neck computed tomography [CT], or positron emission tomography [PET]) includes a history, physical examination, neck ultrasonography, and measurement of serum thyroid-stimulating hormone (TSH). Thyroid scintigraphy should be performed in patients with a subnormal serum TSH concentration. If the serum TSH concentration is normal or elevated and the nodule meets sonographic criteria for sampling (table 3), palpation or ultrasound-guided fine needle aspiration (FNA) biopsy should be performed (algorithm 1). FNA biopsy is the most accurate method for evaluating thyroid nodules and selecting patients for thyroid surgery. Nodules that do not meet sonographic criteria for FNA should be monitored. The frequency of evaluation depends upon the sonographic features of the nodules. Solid hypoechoic nodules and nodules with suspicious sonographic appearance (irregular margins, microcalcifications, taller than wide shape, rim calcifications, or evidence of extrathyroidal extension) should be biopsied when ≥1 cm (as determined by largest dimension). Nodules with sonographic appearance suggesting a low risk for thyroid cancer can be biopsied when larger (≥1.5 to 2 cm). Spongiform nodules ≥2 cm could also be evaluated by FNA, although observation without FNA is an alternative option. FNA biopsy of thyroid nodules is commonly performed under ultrasound guidance. Ultrasound-guided FNA biopsy should be performed for nonpalpable nodules and for nodules that are technically difficult to aspirate using palpation methods alone, such as predominantly cystic or posteriorly located nodules. In patients with large nodules (\>4 cm), ultrasound-guided FNA directed at several areas within the nodule may reduce the risk of a false negative biopsy. Where available, we suggest using an mRNA classifier system (gene expresser classifier), mutational analysis (using a broad next-generation sequencing assay with an expanded panel of point mutations and gene fusions), or combined testing for further evaluating FNA aspirates with indeterminate cytology (follicular lesion/atypia of undetermined significance [FLUS/AUS]) or follicular neoplasm.]

Answer 12

* Lobectomy due to 10% risk of malignancy * If pathology shows adenoma or follicular cell hyperplasia then nothing else is needed * If pathology shows **follicular cancer** then a **total thyroidectomy** should be performed for lesions \> 1cm or lesions with extrathyroidal disease * **¹³¹I** should be given 4-6 weeks after total thyroidectomy [Follicular adenomas (colloid, embryonal, fetal) have no increased cancer risk but lobectomy is still required to prove it is an adenoma.]

Answer 13

Inhibition of organic coupling of iodide in response to administration of high doses of iodine (Lugol's solution, potassium iodide), resulting in less T3 and T4 release [Very effective for thyroid storm.] [UpToDate: The key factor that protects organisms against wide variations in dietary intake of iodine is autoregulation by thyroid follicular cells. Sudden exposure to excess serum iodide inhibits organification of iodide, thereby diminishing hormone biosynthesis; this phenomenon is called the Wolff-Chaikoff effect. However, within two to four weeks of continued exposure to excess iodide, iodide organification and thyroid hormone biosynthesis resume in a normal fashion. Studies in experimental animals suggest that this escape from the Wolff-Chaikoff effect results from decreased trapping of iodide and, therefore, restoration of the intrathyroidal iodide pool to its normal value, even though serum iodide concentrations remain elevated. The mechanism for this escape is unknown but may relate, in part, to decreases in iodide trapping brought about by a fall in sodium/iodide symporter (NIS) activity.]

Answer 14

* ¹³¹I: **Papillary** and **follicular** thyroid cancer * XRT: **Papillary**, **follicular**, **medullary**, and **Hurthle cell** thyroid cancer [¹³¹I can cure bone and lung metastases. It is given **4-6 weeks after surgery** when TSH levels are highest. **Do not give thyroid replacement until after treatment with ¹³¹I** as it would suppress TSH and uptake of ¹³¹I.]

Answer 15

* What percent of individuals have a pyramidal lobe of the thyroid? **10%** * What is a lingual thyroid? **Thyroid tissue** that persists in the foramen cecum at the **base of the tongue** (Only thyroid tissue in 70% of patients who have it) * What is the risk of malignancy in lingual thyroid? **2%** [Treatment for lingual thyroid thyroxine suppression and ¹³¹I ablation. Resect if worried about cancer or if it does not shrink after medical therapy.]

Answer 16

1. **Superior thyroid artery**: 1st branch of the **external carotid artery** 2. **Inferior thyroid artery**: Branch of the **thyrocervical trunk** 3. **Ima artery:** Originates from the **innominate artery** or the **aorta** [The ima goes to the isthmus and is only present in 1% of cases.]

Answer 17

Ligament of Berry

22: Thyroid Flashcards

(41 cards)