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Term 2 > Thyroid (Hi Res) > Flashcards

Thyroid (Hi Res) Flashcards

1
Q

Where is the thyroid gland?

A
  • in front of larynx and trachea

- C5, 6, 7 and T1

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2
Q

Is the thyroid gland vascular?

A

-highly

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3
Q

How many grams is the thyroid gland?

A

25g

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4
Q

What is the thyroid gland surrounded by?

A

-fibrous capsule

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5
Q

How big are the lobes of the thyroid?

A

5cm x 3cm

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6
Q

Lingual Thyroid

A
  • thyroid tissue embedded in the tongue
  • usually asymptomatic
  • no thyroid gland in neck
  • if it becomes large: dysphagia (difficulty swallowing), dysphonia (difficulty speaking) or dyspnea (difficulty breathing)
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7
Q

Arterial Blood Supply of the Thyroid Gland

A

-superior and inferior thyroid arteries

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8
Q

Superior Thyroid Artery

A

-branch of ECA

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9
Q

Inferior Thyroid Artery

A

-branch of SCA

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10
Q

Venous Return of the Thyroid Gland

A

-thyroid veins drain into IJV

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11
Q

Parathyroid Glands

A

-lie again the posterior surface of each thyroid lobe (sometimes embedded in tissue)

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12
Q

Where does the recurrent laryngeal nerve pass?

A

-toward the lobes (near the Rt side near the inferior thyroid artery)

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13
Q

What are the lateral borders of the thyroid gland?

A
  • CCA’s

- SCM muscles

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14
Q

What are the anterolateral borders of the thyroid gland?

A

-jugular veins

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15
Q

What are the anterior borders of the thyroid gland?

A

-strap muscles

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16
Q

What is the posterior border of the longus colli muscle?

A

-longus colli muscles

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17
Q

What is iodine essential for?

A

-formation of thyroid hormones (thyroxine T4, triiodothyronine T3)

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18
Q

What is the bodies main dietary source of iodine?

A
  • seafood

- vegetables grown in iodine rich soil and iodinated table salt

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19
Q

What is the minimum intake of iodine a day?

A

150 ug/day

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20
Q

Iodine Trapping

A

-thyroid gland selectively takes up iodine from the blood

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21
Q

What stimulates the release of T3 and T4 into the blood?

A

-thyroid stimulating hormone (TSH) from the anterior pituitary

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22
Q

What is secretion of TSH stimulated by?

A

-thyrotrophin releasing hormone (TRH) from the hypothalamus

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23
Q

What do increased levels of T3 and T4 decrease?

A

-TSH secretion

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24
Q

What do decreased levels of TSH secretion increase?

A

-T3 and T4 levels

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25
Q

How do T3 and T4 affect most body cells?

A
  • increasing metabolic rate and heat production

- regulating metabolism of carbohydrates, proteins and fats

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26
Q

What are T3 and T4 essential for?

A

-normal growth and development (skeletal and nervous)

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27
Q

Hyperthyroidism

A

-increased T3 and T4

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28
Q

Hypothyroidism

A

-decreased T3 and T4

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29
Q

Symptoms of Hyperthyroidism

A
  • increased basal metabolic rate
  • weight loss
  • good appetite
  • anxiety
  • physical restlessness
  • mental excitability
  • hair loss
  • tachycardida
  • palpitations
  • atrial fibrillation
  • warm, sweaty skin
  • heat intolerance
  • diarrhea
  • grave’s disease
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30
Q

Symptoms of Hypothyroidism

A
  • decreased basal metabolic rate
  • weight gain
  • anorexia
  • depression
  • psychosis
  • mental slowness
  • lethargy
  • dry skin
  • brittle hair
  • bradycardia
  • dry, cold skin
  • prone to hypothermia
  • constipation
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31
Q

What is the first line test for assessment of thyroid function and who is it used on?

A

TSH

  • monitoring patients on thyroid replacement therapy
  • more sensitive than free T4 to alterations of thyroid status in patients with primary thyroid disease
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32
Q

What do high levels of TSH indicate?

A

-hypothyroidism

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33
Q

What do low levels of TSH indicate?

A

-hyperthyroidism

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34
Q

T4 Tests

A
  • investigation of thyroid function

- monitoring patients on thyroid replacement therapy

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35
Q

What happens to T4 with hyperthyroidism?

A

-elevated

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36
Q

Antibodies (anti-TPO Ab) Thyroid Function Tests

A

-marker for diagnosis and management of autoimmune thyroid disease

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37
Q

What could elevated levels of anti-TPO Ab be?

A
  • hashimoto’s thyroiditis

- grave’s disease (85%)

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38
Q

What is anti-TPO Ab?

A
  • thyroid peroxidase (TPO)
  • enzyme made in thyroid gland
  • converts T3 to T4
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39
Q

Where are the thyroid glands embedded?

A

-posterior surface of each thyroid lobe

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40
Q

What are parathyroid glands surrounded by?

A

-fine connective tissue capsules

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41
Q

What do the parathyroid glands secrete?

A

-parathyroid hormone (PTH, parahormone)

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42
Q

What is the main function of PTH

A

-increase blood calcium level

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43
Q

What do blood calcium levels help with?

A
  • muscle contraction
  • nerve transmission
  • blood clotting
  • normal action of enzymes
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44
Q

Which 2 hormones act together to maintain blood calcium levels?

A
  • parathormone

- calcitonin

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45
Q

Fine Needle Aspiration (FNA)

A
  • evaluation of thyroid nodules
  • high accuracy
  • decreased unnecessary operative procedures in patients with benign nodules
  • increased the probability that surgery will be performed on those with malignant disease
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46
Q

FNA of thyroid nodules can be used to categorize tissue into the following categories…

A
  • malignant
  • benign
  • thyroiditis
  • follicular neoplasm
  • suspicious
  • non diagnostic
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47
Q

Thyroid Nodule

A

-region of parenchyma monographically distinct from the remainder of the thyroid

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48
Q

What do we do if a nodule is detected?

A
  • size in 3 dimensions

- location (upper pole, mid gland or lower pole)

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49
Q

Sonographic Features for Differential Diagnosis

A
  • nodule echogenicity
  • morphology
  • cystic change
  • echogenic foci with comet tail artifact (colloid)
  • calcifications
  • flow pattern (peripheral or central)
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50
Q

Echogenicity of Thyroid Carcinoma’s

A

-hypoechoic

51
Q

Cystic Changes and Ring Down Artifact

A

-thyroid cancer is not common in predominantly cystic nodules

52
Q

Vascularity of Benign Nodules

A

-peripheral flow pattern

53
Q

Vascularity of Malignant Nodules

A

-internal vascularity

54
Q

What does an extension of a mass beyond the thyroid capsule into trachea or muscle suggest?

A

-aggressive malignancy

55
Q

Suspicious Features of a Local Lymohadenopathy

A
  • rounded shape
  • loss of fatty hilum
  • cystic change
  • microcalcifications
  • irregular internal hypervascularity
56
Q

2 Most Reliable Benign Features

A
  • near complete cystic appearance

- ring down artifact in colloid cysts/nodules

57
Q

What causes abnormal thyroid function?

A
  • thyroid disease
  • disorders of pituitary or hypothalamus
  • insufficient dietary iodine
  • high/low metabolic rate
58
Q

Hyperthyroidism

A
  • aka thyrotoxicosis
  • excessive levels of T3 or T4
  • due to increased basal metabolic rate
59
Q

In older adults, what is a common consequence of hyperthyroidism?

A
  • cardiac failure

- aging heart works harder to deliver more blood and nutrients to hyperactive body cells

60
Q

Causes of Hyperthyroidism

A
  • graves disease
  • toxic nodular goiter
  • adenoma (benign tumor)
61
Q

When does hypothyroidism occur?

A

Insufficient T3 and T4 secretion causing:

  • congenital hypothyroidism in children
  • myxoedema in adults
62
Q

Congenital Hypothyroidism

A
  • aka cretinism

- profound deficiency/absence of thyroid hormones (becomes evident a few weeks/months after birth)

63
Q

What does absence of thyroid hormones result in?

A

-impairment of growth and mental development

64
Q

What happens is congenital hypothyroidism is not treated?

A
  • permanent mental impairment
  • short limbs
  • large tongue
  • dry skin
  • poor muscle tone
  • umbilical hernia
65
Q

Which pop. and gender is myxoedema most common in?

A
  • elderly

- 5x more common is females

66
Q

Myxoedema

A
  • deficiency of T3 and T4 (low metabolic rate)

- accumulation of polysaccharide substances in the subcutaneous tissues (especially face)

67
Q

Common Causes of Myxoedema

A
  • autoimmune thyroiditis
  • iodine deficiency
  • healthcare interventions (antithyroid drugs, ionizing radiation, surgical removal of thyroid)
68
Q

Graves Disease

A
  • aka graves thyroiditis

- autoimmune disorder (antibody that mimics the effects of TSH is produced)

69
Q

75% of cases of hyperthyroiditis are ______.

A

-graves disease

70
Q

What does graves disease cause?

A
  • increased release of T3 and T4 (signs of hyperthyroidism)
  • goitre (visible enlargement of the gland) as the antibody stimulates thyroid growth
  • exophthalmos
71
Q

Which gender does graves disease more commonly affect?

A

-more women than men

72
Q

Graves Disease on US

A

-diffusely enlarged hypervascular thyroid gland

73
Q

Exophthalmos

A
  • protrusion of the eyeballs
  • due to deposits of excess fat and fibrous tissue behind eyes
  • graves’ disease
  • does not occur in other forms of hyperthyroidism
74
Q

De Quervain’s Thyroiditis

A
  • aka subacute graniulomatous (de queurvain’s) thyroiditis

- painful

75
Q

What is De Quervain’s Thyroiditis associated with?

A

-clinical course of hyperthyroidism, hypothyroidism and return to normal thyroid function

76
Q

De Quervain’s Thyroiditis on US

A
  • diffusely enlarged, poor marginated gland

- colour doppler is normal or decreased

77
Q

How can you distinguish Graves’ disease from De Quervain’s Thyroiditis on US?

A

Graves’ disease- very vascular

De Quervain’s Thyroiditis- normal/decreased vascularity

78
Q

Toxic Nodular Goitre

A

-1 or 2 nodules of a gland that is already affected by goitre secretes excess T3 and T4 causing the effects of hyperthyroidism

79
Q

Is toxic nodular goitre more common in women and men after middle age?

A

-more common in women than men

80
Q

Due to the older age group that toxic nodular goitre affects, what is a more common side affect?

A
  • arrythmias

- cardiac failure

81
Q

Does exophthalmos occur with toxic nodular goitre?

A

No.

82
Q

Autoimmune Thyroiditis/Hashimoto’s Disease

A
  • most common cause of hypothyroidism
  • more common in women
  • organ autoimmune condition
  • goitre may be present
83
Q

Hashimoto’s Thyroiditis on US

A
  • course echotexture
  • innumerable tiny hypoechoic nodule, interspersed with echogenic fibrous bands
  • vascularity may be increased, decreased or normal
84
Q

Adenoma

A

-hyperplastic nodule (aka colloid or adenomatous nodule)

85
Q

What is the most common lesion of the thyroid?

A

-adenoma

86
Q

Adenoma on US

A
  • usually isoechoic (can be hypo)
  • cystic and hemorrhagic degeneration
  • larger, solid masses may be echogenic
  • degeneration of hyper plastic nodules (dystrophic internal or peripheral calcifications)
87
Q

Goiter

A

-enlargement of thyroid gland (no signs of hyperthyroidism)

88
Q

What causes goitre?

A
  • low levels of T3 and T4 stimulate secretion of TSH (results in hyperplasia of gland)
  • hyperthyroidism develops
89
Q

What causes goitre?

A
  • persistant/dietary idoine deficiency (endemic goitre)
  • genetic abnormality affecting synthesis of T3 and T4
  • iatrogenic (ex. antithyroid drugs, surgical removal of excess thyroid tissue)
90
Q

What can an enlarged thyroid gland cause?

A

-pressure damage to adjacent tissues

91
Q

What structures are most. commonly affected by an enlarged thyroid gland?

A
  • oedophagus = dysphagia
  • trachea = dyspnoea
  • reccurent laryngeal nerve = hoarseness of voice
92
Q

Multinodular Goitre

A

-multiple hyperplastic nodules with varying degrees of colloid, necrosis or hemorrhage

93
Q

Multinodular Goitre on US

A
  • heterogenous
  • multiple masses
  • varying size and echotexture
94
Q

Are malignant tumors of the thyroid gland common?

A

No, they are very rare.

95
Q

What is the only well established risk factor for differentiated thyroid cancer?

A

-external head and neck radiation (especially in infants)

96
Q

What is the most common thyroid malignancy?

A
  • papillary cancer

- 75 to 80% of thyroid cancers

97
Q

What is the most specific sonographic finding of papillary cancer?

A

-microcalcifications

98
Q

Sonographic Appearance of Papillary Carcinoma

A
  • solid (87%)
  • hypoechoic (86%)
  • intrinsic vascularity
99
Q

Follicular Neoplasms

A
  • encapsulated true neoplasms of thyroid gland

- 5 to 10% of all thyroid nodules

100
Q

How can we differentiate follicular adenoma’s from follicular carcinoma’s?

A
  • presence of a capsular or vascular invasion on histological exam
  • cannot be made by US
101
Q

Follicular Adenoma’s and Follicular Carcinoma’s on US

A
  • solitary encapsulated tumors
  • well defined hypoechoic halo (fibrous capsule)
  • minimally invasive will be encapsulated
  • invasive will go beyond capsule into vessels and parenchyma
102
Q

Follicular Neoplasms on US

A
  • variable echogenicity
  • smooth
  • ovoid
  • “pseudotesticle”
103
Q

Medullary Thyroid Cancer

A
  • neuroendocrine tumor

- arising from the parafollicular C cells located int he upper 2 3rds of thyroid gland

104
Q

Medullary Carcinoma’s on US

A
  • solid
  • hypoechoic
  • central calcifications
105
Q

Anaplastic Carcinoma

A
  • rare (<1% of all thyroid cancers)
  • aggressive
  • elderly with history of goitre
  • rapidly growing neck mass
  • tumor invades
106
Q

Anaplastic Carcinoma on US

A
  • lg (5 to 10cm)
  • fixed
  • hard
  • heterogenous
  • internal calcifications
  • cystic/necrotic areas
  • lg lymph nodes
107
Q

Lymphoma

A
  • primary is uncommon
  • most are non hodgkin lymphoma’s
  • rapidly enlarging painless neck mass
108
Q

Lymphoma on US

A
  • hypoechoic

- pseudocystic pattern

109
Q

Metastic Disease

A
  • rare
  • solid
  • non calcified
  • hypoechoic nodules
  • hypervascular
110
Q

Hyperparathyroidism

A
  • excessive secretion of parathyroid hormone (PTH), usually by benign tumors of the gland
  • causes release of calcium from bones, raising calcium levels (hypercalcaemia)
111
Q

Effects oh Hyperparathyroidism

A
  • polyuria and polydipsia
  • formation of renal calculi
  • anorexia
  • constipation
  • muscle weakness
  • fatigue
112
Q

2 Types of Hyperparathyroidism

A

1) primary (originates in the thyroid)

2) secondary (originates elsewhere and migrates to the thyroid)

113
Q

Primary Hyperparathyroidism

A

-enlargement of 1 or more of the parathyroid glands causes overproduction of the hormone, resulting in hypercalcemia (high calcium in blood)

114
Q

In approx. 85% of cases, primary hyperparathyroidism is caused by a ______ adenoma.

A

-single

115
Q

Secondary Hyperparathyroidism

A
  • result of another disease
  • low levels of calcium
  • increased parathyroid hormone
116
Q

Tertiary Hyperparathyroidism

A
  • excessive secretion of parathyroid hormone after longstanding secondary hyperparathyroidism
  • results in hypercalcemia
  • persists after successful renal transplant
117
Q

Causes of Tertiary Hyperparathyroidism

A
  • low blood calcium levels (not enough in diet/too much lost in urine)
  • increased phosphate levels
  • kidney failure
  • vitamin D disorders
  • malabsorption (problems absorbing nutrients from food)
118
Q

Results of Tertiary Hyperparathyroidism

A
  • increased risk of bone fractures
  • high BP and heart disease
  • kidney sones
  • osteitis fibrosa
119
Q

Low Blood Calcium Causes

A
  • tetany
  • psychiatric disturbances
  • paraesthesia
  • grand mal seizures
  • cataracts
  • brittle nails
120
Q

Hypoparathyroidism

A
  • parathyroid hormone (PTH) deficiency causes hypocalcaemia (low blood calcium levels)
  • less common than hyperparathyroidism
121
Q

Causes of Hypoparathyroidism

A
  • damage/removal of glands during thyroidectomy
  • ionising radiation
  • development of autoantibodies to PTH and parathyroid cells
  • congenital abnormality of glands
122
Q

Tetany

A

-strong, painful spasms of skeletal muscles, causing benign inward of hands, forearms and feet

123
Q

What causes tetany?

A

-hypocalcaemia (because low blood calcium levels increase excitability of peripheral nerves)

124
Q

What is hypocalcaemia associated with?

A
  • hypoparathyroidism
  • vitamin D deficiency
  • calcium deficiency
  • chronic renal failure
  • alkalosis
  • acute pancreatitis

Term 2 (19 decks)

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