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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
How do T3 and T4 affect most body cells?
- increasing metabolic rate and heat production | - regulating metabolism of carbohydrates, proteins and fats
26
What are T3 and T4 essential for?
-normal growth and development (skeletal and nervous)
27
Hyperthyroidism
-increased T3 and T4
28
Hypothyroidism
-decreased T3 and T4
29
Symptoms of Hyperthyroidism
- 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
30
Symptoms of Hypothyroidism
- decreased basal metabolic rate - weight gain - anorexia - depression - psychosis - mental slowness - lethargy - dry skin - brittle hair - bradycardia - dry, cold skin - prone to hypothermia - constipation
31
What is the first line test for assessment of thyroid function and who is it used on?
TSH - monitoring patients on thyroid replacement therapy - more sensitive than free T4 to alterations of thyroid status in patients with primary thyroid disease
32
What do high levels of TSH indicate?
-hypothyroidism
33
What do low levels of TSH indicate?
-hyperthyroidism
34
T4 Tests
- investigation of thyroid function | - monitoring patients on thyroid replacement therapy
35
What happens to T4 with hyperthyroidism?
-elevated
36
Antibodies (anti-TPO Ab) Thyroid Function Tests
-marker for diagnosis and management of autoimmune thyroid disease
37
What could elevated levels of anti-TPO Ab be?
- hashimoto's thyroiditis | - grave's disease (85%)
38
What is anti-TPO Ab?
- thyroid peroxidase (TPO) - enzyme made in thyroid gland - converts T3 to T4
39
Where are the thyroid glands embedded?
-posterior surface of each thyroid lobe
40
What are parathyroid glands surrounded by?
-fine connective tissue capsules
41
What do the parathyroid glands secrete?
-parathyroid hormone (PTH, parahormone)
42
What is the main function of PTH
-increase blood calcium level
43
What do blood calcium levels help with?
- muscle contraction - nerve transmission - blood clotting - normal action of enzymes
44
Which 2 hormones act together to maintain blood calcium levels?
- parathormone | - calcitonin
45
Fine Needle Aspiration (FNA)
- 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
46
FNA of thyroid nodules can be used to categorize tissue into the following categories...
- malignant - benign - thyroiditis - follicular neoplasm - suspicious - non diagnostic
47
Thyroid Nodule
-region of parenchyma monographically distinct from the remainder of the thyroid
48
What do we do if a nodule is detected?
- size in 3 dimensions | - location (upper pole, mid gland or lower pole)
49
Sonographic Features for Differential Diagnosis
- nodule echogenicity - morphology - cystic change - echogenic foci with comet tail artifact (colloid) - calcifications - flow pattern (peripheral or central)
50
Echogenicity of Thyroid Carcinoma's
-hypoechoic
51
Cystic Changes and Ring Down Artifact
-thyroid cancer is not common in predominantly cystic nodules
52
Vascularity of Benign Nodules
-peripheral flow pattern
53
Vascularity of Malignant Nodules
-internal vascularity
54
What does an extension of a mass beyond the thyroid capsule into trachea or muscle suggest?
-aggressive malignancy
55
Suspicious Features of a Local Lymohadenopathy
- rounded shape - loss of fatty hilum - cystic change - microcalcifications - irregular internal hypervascularity
56
2 Most Reliable Benign Features
- near complete cystic appearance | - ring down artifact in colloid cysts/nodules
57
What causes abnormal thyroid function?
- thyroid disease - disorders of pituitary or hypothalamus - insufficient dietary iodine - high/low metabolic rate
58
Hyperthyroidism
- aka thyrotoxicosis - excessive levels of T3 or T4 - due to increased basal metabolic rate
59
In older adults, what is a common consequence of hyperthyroidism?
- cardiac failure | - aging heart works harder to deliver more blood and nutrients to hyperactive body cells
60
Causes of Hyperthyroidism
- graves disease - toxic nodular goiter - adenoma (benign tumor)
61
When does hypothyroidism occur?
Insufficient T3 and T4 secretion causing: - congenital hypothyroidism in children - myxoedema in adults
62
Congenital Hypothyroidism
- aka cretinism | - profound deficiency/absence of thyroid hormones (becomes evident a few weeks/months after birth)
63
What does absence of thyroid hormones result in?
-impairment of growth and mental development
64
What happens is congenital hypothyroidism is not treated?
- permanent mental impairment - short limbs - large tongue - dry skin - poor muscle tone - umbilical hernia
65
Which pop. and gender is myxoedema most common in?
- elderly | - 5x more common is females
66
Myxoedema
- deficiency of T3 and T4 (low metabolic rate) | - accumulation of polysaccharide substances in the subcutaneous tissues (especially face)
67
Common Causes of Myxoedema
- autoimmune thyroiditis - iodine deficiency - healthcare interventions (antithyroid drugs, ionizing radiation, surgical removal of thyroid)
68
Graves Disease
- aka graves thyroiditis | - autoimmune disorder (antibody that mimics the effects of TSH is produced)
69
75% of cases of hyperthyroiditis are ______.
-graves disease
70
What does graves disease cause?
- increased release of T3 and T4 (signs of hyperthyroidism) - goitre (visible enlargement of the gland) as the antibody stimulates thyroid growth - exophthalmos
71
Which gender does graves disease more commonly affect?
-more women than men
72
Graves Disease on US
-diffusely enlarged hypervascular thyroid gland
73
Exophthalmos
- 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
De Quervain's Thyroiditis
- aka subacute graniulomatous (de queurvain's) thyroiditis | - painful
75
What is De Quervain's Thyroiditis associated with?
-clinical course of hyperthyroidism, hypothyroidism and return to normal thyroid function
76
De Quervain's Thyroiditis on US
- diffusely enlarged, poor marginated gland | - colour doppler is normal or decreased
77
How can you distinguish Graves' disease from De Quervain's Thyroiditis on US?
Graves' disease- very vascular De Quervain's Thyroiditis- normal/decreased vascularity
78
Toxic Nodular Goitre
-1 or 2 nodules of a gland that is already affected by goitre secretes excess T3 and T4 causing the effects of hyperthyroidism
79
Is toxic nodular goitre more common in women and men after middle age?
-more common in women than men
80
Due to the older age group that toxic nodular goitre affects, what is a more common side affect?
- arrythmias | - cardiac failure
81
Does exophthalmos occur with toxic nodular goitre?
No.
82
Autoimmune Thyroiditis/Hashimoto's Disease
- most common cause of hypothyroidism - more common in women - organ autoimmune condition - goitre may be present
83
Hashimoto's Thyroiditis on US
- course echotexture - innumerable tiny hypoechoic nodule, interspersed with echogenic fibrous bands - vascularity may be increased, decreased or normal
84
Adenoma
-hyperplastic nodule (aka colloid or adenomatous nodule)
85
What is the most common lesion of the thyroid?
-adenoma
86
Adenoma on US
- 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
Goiter
-enlargement of thyroid gland (no signs of hyperthyroidism)
88
What causes goitre?
- low levels of T3 and T4 stimulate secretion of TSH (results in hyperplasia of gland) - hyperthyroidism develops
89
What causes goitre?
- 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
What can an enlarged thyroid gland cause?
-pressure damage to adjacent tissues
91
What structures are most. commonly affected by an enlarged thyroid gland?
- oedophagus = dysphagia - trachea = dyspnoea - reccurent laryngeal nerve = hoarseness of voice
92
Multinodular Goitre
-multiple hyperplastic nodules with varying degrees of colloid, necrosis or hemorrhage
93
Multinodular Goitre on US
- heterogenous - multiple masses - varying size and echotexture
94
Are malignant tumors of the thyroid gland common?
No, they are very rare.
95
What is the only well established risk factor for differentiated thyroid cancer?
-external head and neck radiation (especially in infants)
96
What is the most common thyroid malignancy?
- papillary cancer | - 75 to 80% of thyroid cancers
97
What is the most specific sonographic finding of papillary cancer?
-microcalcifications
98
Sonographic Appearance of Papillary Carcinoma
- solid (87%) - hypoechoic (86%) - intrinsic vascularity
99
Follicular Neoplasms
- encapsulated true neoplasms of thyroid gland | - 5 to 10% of all thyroid nodules
100
How can we differentiate follicular adenoma's from follicular carcinoma's?
- presence of a capsular or vascular invasion on histological exam - cannot be made by US
101
Follicular Adenoma's and Follicular Carcinoma's on US
- solitary encapsulated tumors - well defined hypoechoic halo (fibrous capsule) - minimally invasive will be encapsulated - invasive will go beyond capsule into vessels and parenchyma
102
Follicular Neoplasms on US
- variable echogenicity - smooth - ovoid - "pseudotesticle"
103
Medullary Thyroid Cancer
- neuroendocrine tumor | - arising from the parafollicular C cells located int he upper 2 3rds of thyroid gland
104
Medullary Carcinoma's on US
- solid - hypoechoic - central calcifications
105
Anaplastic Carcinoma
- rare (<1% of all thyroid cancers) - aggressive - elderly with history of goitre - rapidly growing neck mass - tumor invades
106
Anaplastic Carcinoma on US
- lg (5 to 10cm) - fixed - hard - heterogenous - internal calcifications - cystic/necrotic areas - lg lymph nodes
107
Lymphoma
- primary is uncommon - most are non hodgkin lymphoma's - rapidly enlarging painless neck mass
108
Lymphoma on US
- hypoechoic | - pseudocystic pattern
109
Metastic Disease
- rare - solid - non calcified - hypoechoic nodules - hypervascular
110
Hyperparathyroidism
- excessive secretion of parathyroid hormone (PTH), usually by benign tumors of the gland - causes release of calcium from bones, raising calcium levels (hypercalcaemia)
111
Effects oh Hyperparathyroidism
- polyuria and polydipsia - formation of renal calculi - anorexia - constipation - muscle weakness - fatigue
112
2 Types of Hyperparathyroidism
1) primary (originates in the thyroid) | 2) secondary (originates elsewhere and migrates to the thyroid)
113
Primary Hyperparathyroidism
-enlargement of 1 or more of the parathyroid glands causes overproduction of the hormone, resulting in hypercalcemia (high calcium in blood)
114
In approx. 85% of cases, primary hyperparathyroidism is caused by a ______ adenoma.
-single
115
Secondary Hyperparathyroidism
- result of another disease - low levels of calcium - increased parathyroid hormone
116
Tertiary Hyperparathyroidism
- excessive secretion of parathyroid hormone after longstanding secondary hyperparathyroidism - results in hypercalcemia - persists after successful renal transplant
117
Causes of Tertiary Hyperparathyroidism
- 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
Results of Tertiary Hyperparathyroidism
- increased risk of bone fractures - high BP and heart disease - kidney sones - osteitis fibrosa
119
Low Blood Calcium Causes
- tetany - psychiatric disturbances - paraesthesia - grand mal seizures - cataracts - brittle nails
120
Hypoparathyroidism
- parathyroid hormone (PTH) deficiency causes hypocalcaemia (low blood calcium levels) - less common than hyperparathyroidism
121
Causes of Hypoparathyroidism
- damage/removal of glands during thyroidectomy - ionising radiation - development of autoantibodies to PTH and parathyroid cells - congenital abnormality of glands
122
Tetany
-strong, painful spasms of skeletal muscles, causing benign inward of hands, forearms and feet
123
What causes tetany?
-hypocalcaemia (because low blood calcium levels increase excitability of peripheral nerves)
124
What is hypocalcaemia associated with?
- hypoparathyroidism - vitamin D deficiency - calcium deficiency - chronic renal failure - alkalosis - acute pancreatitis

Term 2 (19 decks)

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