Thyroid Flashcards
1
Q
What is the thyroid gland shaped like?
A
Butterfly
2
Q
Where is the thyroid gland located?
A
Anterior neck:
From thyroid cartilage to 3rd tracheal ring.
3
Q
What are the three main areas of the thyroid gland?
A
L+R lobes
Isthmus
4
Q
What is an additional 4th area of the thyroid gland sometimes present?
A
Pyramidal lobe
5
Q
How many people have a pyramidal lobe?
A
45%
6
Q
Where is the isthmus located?
A
Between lobes anteriorly to 2nd and 3rd tracheal rings
7
Q
What is found attached to the back of the thyroid gland?
A
Parathyroid glands
8
Q
What are the four compartments of the neck?
A
Prevertebral fascia
Investing fascia
Pretracheal fascia
Carotid sheaths
9
Q
What muscles are not contained in a fascia compartment?
A
Platysmal muscles
10
Q
What do platysma muscles do and what innervates them?
A
Facial expression
CNVII
11
Q
What is contained in the prevertebral fascia?
A
Vertebrae
Postural neck muscles
12
Q
Where is the investing fascia found?
A
Surrounding the other compartments of the neck
13
Q
What is contained within the investing fascia?
A
Trapezius
Sternocleidomastoid
14
Q
What is contained in the carotid sheaths?
A
Vagus nerve
Deep cervical lymph nodes
Carotid artery
Internal jugular vein
15
Q
What links the carotid sheaths?
A
Retropharyngeal space
16
Q
What is important to know about the retropharyngeal space?
A
Back links with chest lining therefore infection can spread.
17
Q
What is contained within the paratracheal fascia?
A
Oesophagus Trachea Thyroid gland Strap muscles Recurrent laryngeal nerves
18
Q
What are the four strap muscles?
A
Thyrohyoid
Sternothyroid
Sternohyoid
Omohyoid
19
Q
What innervates the strap muscles?
A
Fibres from C1 travelling with hypoglossal- Thyrohyoid
Anas cervicalis from C1-3- Others
20
Q
How many arteries supply the thyroid gland?
A
4 or 5
21
Q
What are the arteries that supply the thyroid gland?
A
R+L superior thyroid
R+L inferior thyroid
Ima artery (not always present)
22
Q
Where do the superior thyroid arteries originate from?
A
Common carotid arteries
23
Q
Where do the inferior thyroid arteries originate from?
A
Subclavian arteries
24
Q
Where does the ima artery originate from?
A
Brachiocephalic artery
25
How many veins drain the thyroid gland?
6
26
What six veins drain the thyroid gland?
R+L Superior thyroid vein
R+L Middle thyroid vein
R+L Inferior thyroid vein
27
Where do the superior and middle thyroid veins originate from?
Internal jugulars
28
Where do the inferior thyroid veins originate from?
Brachiocephalic vein
29
How many groups of lymph nodes drain the thyroid gland?
5
30
What five groups of lymph nodes drain the thyroid gland?
Superior deep cervical lymph nodes
R+L Inferior deep cervical lymph nodes
Paratracheal
Paratracheal
31
Which lymph nodes often metastasise?
Tracheal ones.
32
What two nerves are often impinged by the thyroid gland?
Recurrent laryngeal nerve
| Vagus nerve
33
Where do the recurrent laryngeal nerves run?
In the carotid sheaths then loop under the arch of the aorta (L) and right subclavian artery (R)
34
Where do the vagus nerves run?
In the carotid sheaths beside the pretracheal fascia
35
What vertebra levels does the thyroid gland span?
C5-T1
36
What part of the thyroid gland needs to be moved to perform a tracheostomy?
Isthmus
37
What are the basic units of the thyroid gland?
Follicles
38
What are the two areas of a thyroid follicle?
Follicular cells
| Colloid
39
Where are follicular cells found?
As a single cell layer round the outside of the follicle
40
Where is the colloid found?
In the centre of the follicle
41
What is stored in the colloid?
Thyroglobulin
42
What other cells are found in the follicle?
Parafollicular C cells (rare).
| Little role in humans
43
What chemical does the thyroid gland predominantly use?
Iodine
44
What happens to iodine once it has been taken up into follicular cells?
It is excreted into the colloid along with thyroglobulin where they are conjugated to form T3 and T4.
45
What are the first products of iodine and thyroglobulin conjugation?
MIT
| DIT
46
What happens to MIT and DIT?
Joined together to form T3 and T4
47
What are T3 and T4?
Thyroid hormones.
48
Which thyroid hormone is most abundant?
T4 (makes up 90%)
49
Which thyroid hormone is most active?
T3 (4x more active)
50
What happens to T4 in the tissues?
Converted to T3
51
How is the majority of thyroid hormone transported in the blood?
Bound to proteins
52
What proteins commonly bind thyroid hormone?
Thyroxine binding globulin/TBG (70%)
Thyroxine binding prealbumin/TBPA (20%)
Albumin (5%)
Free thyroid hormone
53
What kind of receptor is the thyroid hormone receptor?
Nuclear
54
What general effects does thyroid hormone have on the body?
```
Increased met
Increased thermogenesis
Increased growth
Aids development
Modifies behaviour
```
55
What effect do thyroid hormones have on metabolism?
Increase it
56
How do thyroid hormones increase metabolism?
Increase mitochondria
Mobilize fats
Build protein
Increase blood glucose
57
What effect do thyroid hormones have on thermogenesis?
Increase it
58
How do thyroid hormones increase thermogenesis?
Increase electron uncoupling
59
What effect do thyroid hormones have on growth?
Increase it
60
How do thyroid hormones increase growth?
Increase release of GHSH
61
Is thyroid hormone important for foetal brain development?
Yes
62
What affect does thyroid hormone have on behaviour?
Can cause Permissive Sympathomimetic activity
63
What is Permissive Sympathomimetic activity?
Increased sensitivity to adrenalin and noradrenalin bu increasing receptors.
64
What effect does Permissive Sympathomimetic activity
| have?
Increase HR and force
65
How is thyroid hormone release regulated?
Hypothalamus thyrotropin releasing hormone (TRH) stims pit thyroid stimulating hormone (TSH) which stims thyroid hormone release from thyroid.
66
How can thyroid hormones regulate their release?
T3/T4 inhibit TRH and TSH release therefore decreasing further thyroid hormone release.
67
What kind of feedback loop regulated thyroid hormone release?
Negative feedback
68
What external factors can stimulate thyroid hormone release?
Cold- Increases TRH
Stress- Increases TRH and TSH
Circadian rhythm- Levels highest at night
69
Where does thyroid hormone metabolism occur?
All tissues
70
What enzymes cause thyroid metabolism?
Deiodinase 1
Deiodinase 2
Deiodinase 3
71
Where are the individual deoidinases found and what do they do?
D1- Liver and kidneys. T4 -> T3
D2- All tissues. T4 -> T3
D3- T4 -> rT3 to inhibit function
72
Why do we have D1?
Incase D2 fails
73
What are the four broad pathological categories of thyroid disease?
Hypothyroidism
Thyrotoxicosis/Hyperthyroidism
Subclinical thyroid disease
Non-thyroid illness/sick euthyroid syndrome
74
What external factors can decrease thyroid hormone release?
Steroids- inhibit TSH
75
What is Non-thyroid illness/sick euthyroid syndrome?
Disruption of the HPT axis due to systemic illness decreases TSH levels.
76
Why should you not check thyroid hormone levels in a sick patient?
Non-thyroid illness/sick euthyroid syndrome
77
What is subclinical thyroid disease?
Altered TSH levels with no clinical symptoms
78
How do you diagnose subclinical hypothyroidism?
Raised TSH and normal thyroid hormone
79
When do you treat subclinical hypothyroidism?
TSH > 10 and always in pregnancy
80
How do you diagnose subclinical hyperthyroidism?
Low TSH and normal thyroid hormone
81
When do you treat subacute hyperthyroidism?
TSH < 0.1
82
What two conditions is subacute hyperthyroidism associated with?
Osteoporosis
| AF
83
What is hypothyroidism?
Lack of thyroid hormone
84
What are the three categories of hypothyroidism?
Primary
Secondary
Myxoedema
85
Where is the issue in primary hypothyroidism?
Thyroid gland
86
Where is the issue in secondary hypothyroidism?
Pit gland
87
What are the three kinds of primary hypothyroidism?
Goitrous
Non-goitrous
Self-limiting
88
Give some examples of self-limiting primary hypothyroidism
Withdrawal of antithyroid drugs
Subacute thyroiditis with hypothyroidism
Post-partum thyroiditis
89
Give some examples of non-goitrous primary hypothyroidism
Atrophic thyroiditis
Post radiotherapy or surgery
Congenital developmental defects
90
Give some examples of goitrous primary hypothyroidism
```
Chronic thyroiditis/Hashimoto's disease
Dietary lack of iodine
Drug induced
Maternally transmitted
Inherited biosynthetic defects
```
91
What is Chronic thyroiditis/Hashimoto's disease?
Autoimmune destruction of thyroid gland
92
WHat groups is Chronic thyroiditis/Hashimoto's disease most common in?
Women
| Most common hypo in the west
93
How do you test for Chronic thyroiditis/Hashimoto's disease?
Antibody against thyroid peroxidase (TPO)
| T cell infiltration
94
What things can cause secondary hypothyroidism?
```
Infection
Injury
Infiltration
Malignancy
Congenital
Radiotherapy
Drug induced
```
95
What is myxoedema?
Severe hypothyroidism and a medical emergency.
96
What group is mainly affected by myxoedema?
Elderly women
97
How does myxoedema present?
Bradycardia
Heart block
T wave inversion
Prolonged QT intervals
98
How do you treat myxoedema?
ABCDE
Rewarm
Thyroxine- give slowly
99
How do you treat hypothyroidism generally?
Gradually restore levels with levothyroxine.
100
What doses of levothyroxine should you start on?
Young: 50-100 micrograms
Old: 25-50 micrograms
101
How often should you adjust levothyroxine dose at the start?
Every 4 weeks
102
Once thyroid hormone levels are stable how often should they be checked?
12-18 months
103
What is the drug of choice for treating hypothyroidism?
Levothyroxine- Take on an empty stomach and avoid meds containing Ca and Fe
104
What should you use as your guide for restoring thyroid hormone levels?
Primary- TSH levels
| Secondary- fT4 levels
105
What is thyrotoxicosis?
Condition occurring when tissues are exposed to too much thyroid hormone
106
What are some cardiac symptoms of thyrotoxicosis?
Palpitations
Af
Cardiac failure (rare)
107
What are some systemic symptoms of thyrotoxicosis?
```
Tremor
Sweating
Weight loss
Brittle thin hair
Rapid fingernail growth
Muscle weakness
Heat intolerance
```
108
What are some GI symptoms of thyrotoxicosis?
Diarrhoea
109
What are some psychiatric symptoms of thyrotoxicosis?
Anxiety
| Irritability
110
What are some eye symptoms of thyrotoxicosis?
Eyelid retraction
Double vision
Proptosis- bulging eyes seen in Grave's due to fluid retention round orbits.
111
What is a reproductive symptom of thyrotoxicosis?
Lighter less frequent periods
112
What are the five categories of pathology that can cause thyrotoxicosis?
```
Hyperthyroidism
Thyroiditis
Exogenous thyroid hormones
Ectopic thyroid tissue
Thyroid storm/crisis
```
113
What are some causes of ectopic thyroid tissue?
Metastatic thyroid carcinoma
| Struma ovarii
114
What are some causes of exogenous thyroid hormone?
Overtreatment with levothyroxine
| Thyrotoxicosis factitia- intentional levothyroxine OD
115
What is a thyroid storm/crisis?
Medical emergency due to severe hyperthyroidism
116
How does a thyroid storm/crisis present?
Reap and cardiac collapse
Hyperthermia
Exaggerated reflexes
117
How do you treat a thyroid storm/crisis?
```
ABCDE
Ventilation
PTU
Lugol's iodine
Steroids
B-blockers
Fluids
Monitoring
```
118
What are the three broad categories of hyperthyroidism?
Primary
Secondary
Choriocarcinoma
119
What is the most common cause of primary hypothyroidism?
Autoimmune
120
How do you diagnose primary hypothyroidism?
Low fT3/4
High TSH
95% positive for anti-TPO Ab
121
How do you diagnose primary hyperthyroidism?
High fT3/4
| Low TSH
122
What are the four causes of primary hyperthyroidism?
Grave's disease
Hashitoxicosis
Thyroid cancer
Thyroid nodules
123
What is hashitoxicosis?
Hyperthyroidism as a precursor to Hashimoto's disease
124
How common is thyroid cancer?
Very rare
125
What is Grave's disease?
Autoimmune disease where Thyroid stimulating immunoglobulin (TSI) acts like TSH but unchecked by T3/T4
126
What antibody is responsible for Grave's disease?
Thyroid stimulating immunoglobulin (TSI)
127
How does Thyroid stimulating immunoglobulin (TSI) cause Grave's disease?
Acts like TSH but unregulated by T3/T4
128
What are the special signs and symptoms only seen in Grave's disease?
Pretibial myxoedema- very rare
Thyroid acropachy- Severe finger clubbing
Thyroid bruits- Auscultate over thyroid in patients with large goiter
Thyroid eye disease (TED)/Grave's ophthalmopathy (GO)
129
Describe Thyroid eye disease (TED)/Grave's ophthalmopathy (GO)
Occurs in 20% Grave's patients but can predate it
Uni or bi lateral
Worse with smoking
TRAb driven
130
How do you treat Thyroid eye disease (TED)/Grave's ophthalmopathy (GO)?
Mild- Lubricants
| Severe- Steroids, surgery, radiotherapy
131
How do you diagnose Thyroid eye disease (TED)/Grave's ophthalmopathy (GO)?
Low TSH- often 0
High fT3/4
TRAb (TSH receptor Ab)- if raised no need to image
132
What can Thyroid eye disease (TED)/Grave's ophthalmopathy (GO) be associated with?
Cardiac abnormalities
Increased calcium and ALP- gives osteoporosis
Leucopenia (low WCC)
133
What are thyroid nodules?
Lumps of glandular tissue that can secrete excessive thyroid hormones or invade other structures.
134
Describe thyroid nodules
Tend to be symmetrical and may feel nodular. Move with thyroid
135
What are the two forms of thyroid nodule possible?
Solitary
| Multinodular goiter
136
How do you diagnose thyroid nodules?
Low TSH and high fT3/4
TRAb negative
High iodine uptake on imaging
US
137
Give a cause of secondary hyperthyroidism
Thyrotropinoma
138
What causes Thyrotropinoma?
Pit adenoma causing increased TSH release.
139
What is a Choriocarcinoma?
Tumour is uterus which secretes hCG. hCG is structurally similar to TSH therefore get unregulated thyroid stim.
140
How do you treat hyperthyroidism?
Antithyroid drugs
Beta-blockers
Radioiodine
Thyroidectomy
141
What two antithyroid drugs are used?
Carbimazole
| Propythiouracil (PTU)
142
When is Carbimazole used?
1st line- only don't use in 1st trimester
143
When is Propythiouracil (PTU) used?
In the first trimester
144
Why is Carbimazole prefered to PTU?
More potente (once daily dose)
145
Which beta blocker is routinely used in hyperthyroidism and why?
Propranolol- to reduce sympathetic NS stim and inhibits DIO1
146
How do antithyroid drugs work?
Block TPO preventing thyroid uptake (?)
147
What is a rare but dangerous side effect of antithyroid drugs?
Agranulocytosis- 0.5% of patients. Neutrophils stop being produced. Highest risk in first 6 weeks therefore warn patients verbally and in writing to stop and have FBC if have fever, oral ulcer or throat infection.
148
What are the two methods for treating Grave's disease?
Dose titration
| Block and replace
149
What is dose titration?
12-18 months normal hyperthyroidism treatment
150
What is block and replace?
6 months intensive hyperthyroid treatment then replace with levothyroxine
151
What should you do if primary treatment of Grave's disease fails?
Surgery or radioiodine
152
When is radioiodine used?
Relapsed Grave's or nodular disease
153
When should you not use radioiodine?
Pregnancy or thyroid eye disease
154
What is a drawback of radioiodine?
Can cause hypothyroidism
155
When should you do a thyroidectomy?
When radioiodine is contraindicated.
156
What are potential complications of thyroidectomy?
Damage to the recurrent laryngeal nerve and parathyroid glands
157
How do you treat thyroiditis?
Self limiting therefore will resolve with time
158
What are some causes of thyroiditis?
Subacute/de Quervain's thyroiditis
Post-partum thyroiditis
Drug induced- amiodarone
Subacute thyroiditis
159
How does amiodarone cause thyroiditis?
Inhibits DOI1 therefore get increase in T4 and decrease in T3 but normal TSH.
160
How can subacute thyroiditis present?
May be triggered by viral infection
| Neck tenderness, fever etc
161
How do you distinguish a thyroglossal cyst?
Stick tongue out and it moves
162
Describe the goiter seen in Grave's disease?
Smooth and regular
163
How does a Graves goiter present on scanning?
Completely black
164
Describe a toxic multinodular goiter?
Irregular
165
What effect can a hyperthyroid nodule have on the rest of the thyroid gland?
Cause hypothyroidism
166
What is a side effect of radioiodine?
Can get brief surge of hyperthyroidism
Neck pain
2kg weight gain
167
How do you treat Grave's disease?
Radioiodine
Antithyroid drugs
Avoid surgery
168
WHat is the Wolff-Chaikoff effect?
The ability of high dose iodine (KI) to block T4 production in the short term. Only lasts 10-14 days
169
What is the only thyroid disease you tend to get eye involvement with?
Grave's
170
What does a low TSH by itself suggest?
Thyrotoxicosis
171
Can a lymphoma affect the thyroid?
Yes but rarely
172
What physical sign is important to ask about when examining a thyroid lump?
Voice changes
173
What are some potential side effects of Carbimazole?
Minor rash
| Agranulocytosis
174
What are some side effects of PTU?
Liver failure
| Agranulocytosis
175
What should a patient be warned about when taking antithyroid drugs?
Agranulocytosis- if ill stop immediately and get FBC
176
What is a potential problem with thyroxine?
Can have cardio effects therefore if have HD give low dose and work up
177
What is a differential for thyroid swelling?
Enlarged lymph nodes- tend to be more laterally though
