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Pathophys II > Thyroid Lecture > Flashcards

Thyroid Lecture Flashcards

1
Q

The blood supply to the thyroid includes

A

the superior and inferior thyroid arteries

superior, middle, and inferior thyroid veins

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2
Q

The lymphatic drainage of the thyroid includes

A

upper and lower deep cervical lymph node

pretracheal and paratracheal lymph node

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3
Q

The _________ and the external motor branch of the __________ are in intimate proximity to the thyroid gland

A

recurrent laryngeal nerve; superior laryngeal nerve

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4
Q

The thyroid gland consists of

A

two lobes joined by an isthmus

upper isthmus borders the cricoid cartilage

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5
Q

The thyroid gland is innervated by

A

adrenergic** and cholinergic** nervous systems

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6
Q

The thyroid gland takes absorbed

A

exogenous iodide**** (iodine is reduced to iodide in the gut) into the gland and synthesizes 2 hormones

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7
Q

The two thyroid hormones include:

A

triiodothyronine (T3)

Thyroxine (t4) **

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8
Q

Thyroid hormone production is dependent on

A

availability of exogenous iodine**

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9
Q

Iodine is reduced to iodide in the GI tract, absorbed into the blood stream and then is actively transported from

A

the plasma into the thyroid follicular cells***

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10
Q

_________________ are stored in the ______until they are needed and released into circulation

A

T3 & T4 are stored in the colloid

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11
Q

Iodide gets trapped inside the follicular cell and gets compounded with

A

tyrosine and thyroglobulin and yields monoiodotryosine and diiodotyrosine
which are then coupled to form triiodothyronine (T3)* and thyroxine (T4)*

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12
Q

The role of thyroid hormone

A

affects virtually all metabolic processes in the body

  • regulates carbohydrate, lipid, and protein metabolism
  • necessary for fetal development
  • CNS development and activity
  • Bone and tissue growth
  • Gastrointestinal regulation
  • Cardiac myocytes- contractility
  • Vascular smooth muscle- direct vasodilation
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13
Q

Thyroid hormone release is the interaction between

A

hypothalamic-pituitary axis
thyroid gland
and thyroid hormones

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14
Q

The _______ controls the release of thyrotropin-releasing hormone

A

hypothalamus**

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15
Q

In the pituitary gland, the

A

TRH stimulates the secretion of thyroid stimulating hormone*** from the anterior pituitary

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16
Q

TSH acts on the

A

thyroid gland** to enhance synthesis and secretion of T3 & T4

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17
Q

A _______ exists between the hypothalamus, pituitary, and the thyroid gland

A

classic feedback loop**

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18
Q

Increased levels of thyroid hormone

A

INHIBIT**** secretion of TSH from the pituitary

negative feedback loop

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19
Q

Thyroid hormone levels are the primary determinant of

A

TSH secretion

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20
Q

The function of thyroid stimulating hormone is to

A

control production of thyroid hormones thyroxine (T4) & triiodothyronine (T3)
stimulates all aspects of thyroid hormone production- uptake of iodide, iodide incorporation, eventual release of T4 & T3

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21
Q

In hypothyroidism, the TSH level will be

A

ELEVATED ****

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22
Q

In hyperthyroidism, the TSH level will be

A

DECREASED**

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23
Q

10% of triiodothyronine (T3) is synthesized and released by

A

the thyroid gland

-also formed in the liver and kidneys by peripheral conversion of T4 by selenodeiodinases

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24
Q

T3 is ____________ than t4

A

3-4x’s more active*****

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25
Q

The half life of triiodothyronine is

A

1-3 days****

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26
Q

Triiodothyronine is _______ bound to albumin

A

99.7%

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27
Q

_________ of thyroxine (T4) is synthesized and released by the thyroid gland

A

90%

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28
Q

Thyroxine has a serum half life of

A

6-7 days (about 1 week)****

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29
Q

________ % of thyroxine (T4) is bound to thyroid binding globulin

A

99.9

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30
Q

Both T3 and T4 circulate

A

tightly protein bound in the blood stream
T4 is more tightly bound than T3 (leads to its longer half-life)
a larger amount of T3 circulates in the bloodstream compared to T4

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31
Q

It is the ______ form of T3 & T4 that is active and drives patient’s metabolic state

A

free

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32
Q

When analyzing thyroid function tests,

A

it is important to combine both clinical picture with laboratory tests

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33
Q

The principle thyroid function tests include

A

TSH, serum T4, serum T3, radioactive iodine uptake (RAIU)

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34
Q

With aging, there is _________ in baseline TSH

A

an increase

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35
Q

Normal thyroid stimulating hormone (TSH) is

A

0.4-5.0 milliunits/L *****

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36
Q

Subclinical hyperthyroidism is defined as

A

TSH level of 0.1-0.4 milliunits/L with normal levels of free T3 and free T4

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37
Q

Overt hyperthyroidism is defined as

A

TSH level below 0.03 milliunits/L with elevated T3 and T4

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38
Q

Subclinical hypothyroidism is defined as

A

TSH level of 5.0-10 milliunits/L with normal levels of T3 and T4

39
Q

Overt hypothyroidism is defined as

A

a TSH level higher than 20.0 milliunits/L with reduced levels of T3 and T4

40
Q

A diagnosis of pituitary dysfunction can be performed from

A

thyrotropin releasing hormone test- injection of exogenous TRH by rapid IV push
serum concentration of TSH is collected at 15 and 30 min intervals over 2-3 hours
normally TSH would rise in concentration

41
Q

If hypothyroidism is due to pituitary disease (secondary hypothyroidism) administration of TRH

A

does not produce an increase in TSH

42
Q

Thyroid pathophysiology includes

A

hyperthyroidism
hypothyroidism
goiter & thyroid tumors

43
Q

Hyperthyroidism has a wide clinical spectrum ranging from

A

subclinical to life-threatening thyroid storm*

44
Q

Hyperthyroidism laboratory values will display

A

low TSH and high free T4 and T3

45
Q

In subclinical hyperthyroidism the TSH is

A

low but free T4 and free T3 are normal

46
Q

Causes of hyperthyroidism include

A 
Graves disease*** (most common)
toxic multinodular goiter
autonomously functioning thyroid nodule
thyroiditis
exogenous thyroid hormone ingestion
iodine induced
47
Q

Graves disease is an

A

autoimmune disease caused by thyroid-stimulating antibodies that bind to TSH receptors in the thyroid, stimulating thyroid growth, vascularity, and hypersecretion

48
Q

Signs and symptoms of hyperthyroidism include

A

hypermetabolic state

  • anxious, restless, hyperkinetic
  • warm skin, sweating, flushed, heat intolerance
  • protruding eyes (exophthalmos or proptosis)
  • weakness, fatigue, inability to sleep
  • tremors, weight loss, frequent bowel movements
  • increased cardiac work, tachycardia, dysrhythmias, palpitations
49
Q

Increased heart rate as a result of hyperthyroidism can lead to

A

stroke, MI, ectopy, CHF, PVCs, and a fib

50
Q

Hypermetabolism results in

A

-increased CO2 production–> increased minute ventilation–> weakness in respiratory muscles

51
Q

Morbidity and mortality related to hyperthyroidism includes

A

increased HR
hypermetabolism
myopathies

52
Q

Treatment of hyperthyroidism includes

A

antithyroid medications
radioactive iodine
thyroidectomy

53
Q

A thyroidectomy should only be performed after

A

euthyroid state has been achieved with medication

54
Q

Radioactive iodine may be used for

A

recurrent or persistent hyperthyroidism

55
Q

Anti-thyroid medications include

A

thionamides- Propylthiouracil (PTU) or methimazole

interferes with coupling of thyroid hormones in the thyroid

56
Q

Thyroid storm is an

A

acute life-threatening form of hyperthyroidism

significant associated mortality (>20%)

57
Q

The diagnosis of thyroid storm is ffrom

A 
temperature elevation with diaphoresis (as high as 106 degrees)
marked tachycardia (can manifest as afib or Vtach)
cerebral dysfunction (confusion, psychosis, seizures, etc.)
Gastrointestinal disorders (N/V, obstruction)
58
Q

Precipitating events for thyroid storm can include

A

surgery, infection, IV contrast dyes, DKA, trauma, and even vigorous palpation of the thyroid

59
Q

Thyroid storm most often occurs

A

in the postoperative period of inadequately treated hyperthyroid patients

60
Q

Treatment of thyroid storm includes

A

decrease production, conversion, and secretion of thyroid hormone (propylthiouracil, corticosteroids)
supportive care- aggressive tx. of temperature, acid-base abnormalities oxygenation & ventilation, oxygen, hydration- consider glucose containing fluids for hypermetabolism
beta blockers- propranolol, esmolol
determine underlying cause
consider avoiding SNS activation (ketamine, epi, etc.)

61
Q

Preoperative management of anesthesia in the emergent patient with hyperthyroidism includes

A 
good premedication (benzos/narcs)
avoid anticholinergics- may precipitate tachycardia
62
Q

Intraoperative management of anesthesia in the emergent patient with hyperthyroidism includes

A

consider invasive monitoring (e.g. a-line)
-differentiate between MH and thyroid storm
-adequate anesthetic depth to avoid exaggerated SNS response
-avoid ketamine, ephedrine, epinephrine, dopamine due to effect on SNS
hypotension- consider fluids and direct acting vasopressor (phenylephrine)
succs, NDMR, and N2O are okay
eye protection (lubricant, pads)

63
Q

Postoperative management of anesthesia in the emergent patient with hyperthyroidism includes

A

continue beta blocker for 7-8 days

64
Q

Hypothyroidism or myxedema can be

A 
primary hypothyroidism (90-95% of all cases)
autoimmune hypothyroidism
secondary hypothyroidism
65
Q

Describe primary hypothyroidism:

A

decreased production of thyroid hormones despite normal TSH

most common causes are ablation of the gland by radioactive iodine therapy or surgery

66
Q

Describe autoimmune hypothyroidism:

A

autoantibodies block TSH receptors in the thyroid

this immune response destroys receptors (instead of stimulating)

67
Q

Describe secondary hypothyroidism:

A

secondary to hypothalamic or pituitary disease

68
Q

Hashimoto’s thyroiditis is

A

autoimmune disorder, goiter, and hypothyroidism

commonly in middle aged women

69
Q

Signs and symptoms of hypothyroidism include

A

slow, progressive

mild-tires easily, weight gain despite decreased appetite

70
Q

Signs and symptoms of moderate to severe hypothyroidism include

A

fatigue, apathy, listlessness
slow speech
cold intolerance, decreased sweating, constipation, menorrhagia, slow motor function
slowed gastrointestinal function
dry hair, skin, large tongue, periorbital edema
cardiomyopathy, impaired baroreceptor function, bradycardia, hyponatremia
impaired ventilatory response to hypoxia and hypercarbia

71
Q

Describe the diagnosis of primary versus secondary hypothyroidism

A

primary- reduced levels of T4, T3 and elevated TSH

secondary (pituitary)- reduce levels of T4, T3 and reduced TSH

72
Q

A _________ test can confirm pituitary pathology as a cause of hypothyroidism

A

TRH stimulation test
-in primary hypothyroidism basal levels of TSH are elevated and the elevation is exaggerated after TRH administration. With pituitary dysfunction, there is a blunted or absent response to TRH

73
Q

Treatment of hypothyroidism is

A

L-Thyroxine (levothyroxine sodium) “synthroid”**
pharmacology: levothyroxine is a synthetic form of thyroxine
Onset of action: oral 3 to 5 days, peak effect may required 4 to 6 weeks

74
Q

Anesthetic considerations for the patient with hypothyroidism includes ***

A

airway compromise secondary to a swollen oral cavity, edematous vocal cords, or goiter
decreased gastric emptying increases the risk of aspiration
hypodynamic cardiovascular system
decreased ventilatory responsiveness to hypoxia and hypercarbia
risk for hypothermia
hematologic abnormalities
increased sensitivity to sedatives/narcotics

75
Q

Describe the hypodynamic cardiovascular system as it relates to hypothyroidism & anesthetic considerations

A

decreased CO, SV, HR, baroreceptor reflexes, and intravascular volume may be compromised by surgical stress and cardiac-depressant anesthetic agents

76
Q

Describe the hematologic abnormalities as it relates to hypothyroidism and anesthetic considerations

A

anemia, platelet dysfunction, electrolyte imbalances, & hypoglycemia

77
Q

Management of anesthesia in emergency with a patient who has hypothyroidism includes

A

potential for severe intraoperative CV instability & myxedema coma
IV thyroid replacement- IV triiodothyronine is effective in 6 hours
steroid coverage
phosphodiesterase inhibitors such as milrinone may be effective in the tx. of reduced myocardial contrality

78
Q

The mortality rate of myxedema coma is

A

50%

79
Q

Myxedema coma is a

A

medical emergency & requires IV thyroxine or triiodothyronine and IV steroids for possible adrenal insufficiency

80
Q

Myxedema coma most commonly occurs in

A

elderly women with a long history of untreated hypothyroidism

81
Q

Myxedema coma is a

A

rare, severe form of hypothyroidism characterized by delirium or unconsciousness, hypoventilation, hypothermia, bradycardia, hypotension, and a severe dilutional hyponatremia

82
Q

Goiter is the

A

swelling of the thyroid gland

can be a result of hypothyroidism or hyperthyroidism

83
Q

Causes of goiter include

A

deficient intake of iodine
ingestion of a dietary agent (e.g. cassava)
pharmacologic goitrogen
defect in the hormonal biosynthetic pathway

84
Q

Anesthetic management of the patient with goiter includes

A

careful airway evaluation and extreme caution with any respiratory depressants prior to securement of the airway

85
Q

Nontoxic goiters are

A

euthyroid but can lead to toxic multinodular goiter

86
Q

Complications of thyroid surgery includes

A

superior laryngeal nerve injury

recurrent laryngeal nerve injury

87
Q

Superior laryngeal nerve injury results in

A

weakness of the voice in ability to create high tones

88
Q

Recurrent laryngeal nerve injury can be

A

unilateral or bilateral
unilateral= hoarseness
bilateral= airway obstruction, may require tracheostomy
paralysis of the abductor vocal cord muscle results in median/paramedian cord position

89
Q

Ideally, the patient with thyroid issues should be

A

euthyroid prior to any surgical procedure- may require delay of elective surgery for 6-8 weeks

90
Q

Thyroid surgery anesthetic considerations include

A

use of recurrent laryngeal nerve monitor
airway compromise with large goiters may be present with nerve compression, tracheal deviation, and erosion
1-2 months of medication treatment followed by recent TSH and T3/T4 may indicate optimal treatment effectiveness

91
Q

Additional complications of thyroid surgery include

A

tracheal compression & hypoparathyroidism

92
Q

Describe the complication of tracheal compression

A

due to expanding hematoma

hematoma evacuation is first-line treatment- at bedside if necessary

93
Q

Describe the complication of hypoparathyroidism

A

can result from damage to the blood supply of the parathyroid gland, not usually inadvertent removal

  • hypocalcemia 24-48 postoperatively
  • stridor/laryngospasm- treatment is IV calcium

Pathophys II (43 decks)

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