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Flashcards in Chapter 17 Deck (64):
1

How is the thyroid encapsulated?

By a fibrous capsule, which is in turn invested by a false capsular layer arising from the deep cervical fascia (pretracheal fascia)
-The fascial attachment between the gland and the upper two or three tracheal rings is also known as the ligament of Berry

2

Where do the strep muscles reside?

The strep muscles are the sternothyroid and sternohyoid
They reside anterior to the lobes of the gland are innervated by the ansa cervicalis

3

What define the posteromedial borders of the thyroid gland?

The trachea and the esophagus

4

What lies lateral to each lobe of the thyroid?

Common carotid artery
Internal jugular vein

5

What lies medial to each thyroid lobe?

Vagus, in the cleft between the trachea and esophagus, and beneath or embedded in the ligament of Berry

6

Blood supply of the thyroid- general

Predominantly from the paired superior and inferior thyroid arteries

7

Superior thyroid artery

The first branch off the external carotid artery and descends toward the superior pole of the thyroid lobe, where it divides into anterior and posterior branches

8

Inferior thyroid artery

A branch of the thyrocervical trunk and travels posterior to the carotid sheath before it reaches the posterior surface of the mid-portion of the gland
-Also provides the principal blood supply to all 4 parathyroid glands in ~80%

9

Thyroid ima arteries

Present in 5-10% of the population
Arise from the brachiocephalic trunk or directly from the aortic arch and can provide additional blood supply to the thyroid

10

What veins drain the superior poles and lateral aspects of the thyroid, respectively?

Superior and middle veins
Drain into the internal jugular veins

11

What arise from the inferior poles of the thyroid and course anterior to the trachea?

Inferior thyroid veins
Drain into the brachiocephalic veins

12

Lymphatics of the thyroid

Interlobular lymphatics communicate with intrascapular lymphatics
Pretracheal lymph nodes, paratracheal lymph nodes, and the tracheoesophageal lymph nodes along the recurrent laryngeal chain
The supraisthmic pretracheal lymph nodes that run alongside the pyramidal lobe are also known as the delphian nodes
The regional nodal basins are a frequent site of metastatic thyroid cancer?

13

How is the thyroid innervated?

By postganglionic fibers that originate from the cervical sympathetic ganglia

14

RLN

Comprised of all intrinsic laryngeal muscles except for the cricothyroid muscle
Injury leads to hoarseness and difficulty in phonation secondary to paralysis of the ipsilateral vocal cord

15

What does bilateral RLN injury result in?

Abduction of both vocal cords with complete airway obstruction necessitating emergent intubation or tracheostomy

16

Branching of the RLN

Branches from the vagus nerve and loops around the origin of the right subclavian artery to ascend in the tracheoesophageal groove

17

Branching of the left RLN

Branches from the vagus nerve and loops around the aortic arch near the ligamentum arteriosum

18

Nonrecurrent laryngeal nerve on the right side

Present in ~1% of the population and is often associated with an aberrant subclavian artery
A left is much less common and may be associated with a right-sided aortic arch

19

What innervates the cricothyroid muscle?
What can an injury to this nerve result in?

External branch of the superior laryngeal nerve
Loss of vocal projection and volume, particularly at higher pitches

20

Hormones involved in the thyroid

Thyroid hormones
Calcitonin

21

Thyroid function tests

Unlike T4 or T3 levels, which vary depending on the plasma level of TBG, albumin, and prealbumin, serum TSH levels are independent of the concentrations of carrier proteins in the circulation

22

What should be done following adjustment of an oral T4 dosage?

Serum TSH measurement should be delayed for at least 4-8 wks

23

When are TSH levels not reliable indicators of thyroid dysfunction?

In pts who have neuropsychiatric disorders or diseases of the pituitary gland (pituitary adenoma)

24

TRH stimulation test

Check baseline TSH level, administer synthetic TRH, measure TSH level again after 30-60 mins
-Normally, a rise in TSH from baseline is observed after TRH administration
-Pts with hypothyroidism have a blunted response or no rise in TSH

25

Thyroid imaging

US is noninvasive and inexpensive (solid vs cystic)
FNA
Radionuclide imaging- functional assessment of the thyroid gland
-Allows for localization of thyroid tissue, detection of functional metastatic lesions from thyroid cancer, and an estimation of the size of the thyroid gland

26

What can detect areas of calcification in the thyroid?
Identify regions of increased vascularity?

High-resolution u/s
Ultrasonography with Doppler

27

What are three hyperthyroid causes that more commonly require surgical intervention

Graves dz (toxic diffuse goiter)
Toxic nodular goiter
Solitary toxic nodule

28

Possible accompanying sx of hyperthyroid diseases?

Tachycardia
Wt loss
Tremors
Increased anxiety
Sleep disturbances

29

Graves dz

An autoimmune disorder characterized by the presence of antibodies against the TSH receptor on the follicular cell

30

Graves dz is _____ more common in ____ than ____

6-7x
Women
Men

31

Clinical manifestations of Graves dz

Fatigue
Heat intolerance
Wt loss
Diarrhea
Hair loss
Irritability
Tremor
Arrhythmias
HTN
Osteoporosis
Amenorrhea
Sweating

32

Exam of Graves dz

Thyroid gland is typically diffusely enlarged, symmetric, and smooth

33

Tx options for Graves

Medical
Radioactive iodine thyroid ablation
Surgical thyroid ablation

34

Medical therapy for Graves

Aimed at reducing thyroid hormone levels and is the first-line therapy for most pts
Thionamide therapy must be continued for a prolonged period to control thyroid levels and allow for spontaneous remission
Beta blocking agents such as propranolol may be used as adjuvants

35

Radioactive iodine therapy for Graves

Induces long-standing remission in most pts, with relatively few side effects, and is the definitive tx used for most adult pts with Graves dz in the US

36

Advantages and disadvantages for radioactive iodine therapy for Graves

Primary advantage- Does not require an invasive procedure
Disadvantage- high incidence of hypothyroidism

37

Who are not considered candidates for radioactive iodine therapy in Graves disease?

Pregnant women
Pts with concomitant thyroid nodules
Those with very large glands
Generally avoided in children

38

When is operative intervention indicated for Graves?

Pts who are noncompliant with, or intolerant to, antithyroid drug therapy
Those who are refractory to medical therapy
Those with contraindications to radioactive therapy
Those with large glands (greater than or equal 80 g)
Symptomatic compression
Those with concern for malignancy
Pts who are younger than 20 yrs with large goiters

39

What should be done preoperatively for Graves?

Achieve a euthyroid state with administration of pTU in combo with propranolol typically initiated 4-8 wks before operation and continued during and after the operation
Lugol solution can be given to pts to decrease the vascularity of the gland and make it firmer and easier to resect

40

Autonomously functioning thyroid nodules

Function and grow independent of TSH
Appear hot on radionuclide studies
Majority of these nodules enlarge, develop central necrosis, and become nonfunctional

41

Solitary toxic nodules

Have a peak incidence during the fifth decade of life and are much more common in women

42

Toxic multinodular goiter

Accounts for approximately 20% of pts with hyperthyroidism and is most common in women older than 50 yrs

43

Tx of solitary functional nodules

Influenced by size and degree of function, as well as by the pt's age and overall health

44

When to treat toxic nodules surgically

Ones that exceed 3 cm in diameter

45

What is the standard tx for toxic multinodular goiter?

Antithyroid drug therapy, followed by thyroidectomy

46

Presentation of hypothyroid

Fatigue
Wt gain
Brittle nails
Coarse hair
Constipation
Neurocognitive disturbances, such as depression, irritability or impaired memory

47

What is the MC inflammatory condition of the thyroid and the most frequent cause of spontaneous hypothyroidism?

Hashimoto thyroiditis

48

What can occur during the acute phase of Hashimoto thyroiditis?

Transient hyperthyroidism

49

Findings on palpation in Hashimoto thyroiditis

Gland is usually firm and rubbery with a lobulated surface

50

What is usually sufficient to make the dx of Hashimoto thyroiditis?

Elevated antimicrosomal antibody titer, along with a suggestive clinial exam

51

When is thyroidectomy indicated in Hashimoto thyroiditis?

When the gland continues to grow despite thyroid suppression therapy

52

When should a Hashimoto thyroiditis pt be evaluated for lymphoma?

A rapid enlargement of the thyroid gland

53

Acute thyroiditis

An infectious disorder, which is more common in women

54

Organisms of acute thyroiditis

S. pyogenes
S. aureus
P. pneumoniae
Usually spread via the lymphatics from local infectious sources

55

Presentation of acute thyroiditis

Acute onset of neck pain and fever
Pts typically euthyroid

56

Tx of acute thyroiditis

Appropriate IV abx
Surgical drainage if abscess present

57

Subacute thyroiditis

A dz that typically occurs in middle-aged women within wks of an upper respiratory or other viral infection

58

Sx of subacute thyroiditis

Weakness
Depression
Easy fatiguability
Anterior neck pain
Referred pain to the ear or angle of the jaw

59

Exam of subacute thyroidits

Pt usually afebrile
Thyroid firm and extremely TTP
Thyroid may be swollen unilaterally, and the overlying skin is occasionally erythematous

60

Tx of subacute thyroiditis

Typically self-limited and usually resolves within a few mos
Salicylates
NSAIDs
Corticosteroids

61

Riedel struma

A very rare chronic inflammatory proliferative d/o in which the thyroid tissue and frequently the adjacent strap muscles and carotid sheaths are replaced by dense fibrous tissue

62

Presentation of Riedel struma

Pts are most often euthyroid, although hypothyroidism may be seen in up to 30% of pts

63

Workup for Riedel struma

Open bx to r/o thyroid carcinoma or lymphoma

64

Tx of Riedel struma

Often self-limiting
Steroids or tamoxifen is sometimes beneficial
If airway compromise present, surgical therapy with isthmusectomy