thyroid Flashcards
1
Q
what vertebra levels is the thyroid gland
A
C5-T1
2
Q
what is the part called that joins the two lobes of the thyroid
A
isthmus
3
Q
what tracheal cartilages does the isthmus lie anterior to
A
2nd and 3rd
4
Q
how will a lump in the thyroid/enlarged gland move during swallowing
A
superior then inferior
5
Q
what are two anatomical variants of the thyroid gland
A
pyramidal lobe
thyroidea ima
6
Q
where does a pyramidal lobe usually arise
A
from left lateral lobe
7
Q
where does a pyramidal lobe usually attach superiorly
A
thyroid cartilage
8
Q
true/false
all pyramidal lobes are connected to the main gland
A
false - some may not be connected
9
Q
how high may a pyramidal lobe go
A
the hyoid bone
10
Q
what gives the thyroid its parasympathetic innervation
A
CN X
11
Q
what gives the thyroid its sympathetic innervation
A
cervical portion of sympathetic trunk (superior, middle and inferior)
12
Q
from what do the inferior and superior thyroid arteries branch
A
ECA
13
Q
where do the superior and middle thyroid veins drain
A
IJV
14
Q
where does the inferior thyroid vein drain
A
brachiocephalic vein
15
Q
what is the berry ligament
A
attached posterior medial aspect of the gland
16
Q
the thyroid develops from the evagination of the _____ epithelium
A
pharyngeal
17
Q
where does the thyroid begin its development and as what
A
begins as a midline epithelial proliferation at the foramen caecum
18
Q
through what does the thyroid migrate inferiorly
A
thyroglossal duct
19
Q
when does the thyroid reach its final position
A
7th week development
20
Q
what can be found along the thyroglossal duct
A
ectopic tissue (thyroglossal duct cyst)
21
Q
what is the thyroid made up of
A
follicles
22
Q
what makes up a follicle
A
follicular cells enclosing a colloid
23
Q
what is a colloid
A
tyrosine containing thyroglobulin filled sphere
24
Q
what surrounds each follicle
A
flat to cuboidal follicular epithelial cells
25
what are the parafollicular cells and what do they secrete
```
slightly larger cells with clearer cytoplasm
secrete calcitonin (lowers serum Ca but insignificant)
```
26
what is at the centre of each follicle
dense amorphic pink material containing thyroglobulin
27
what do the follicular cells take up
iodine
28
how do follicular cells form MIT and DIT
iodine taken up is attached to tyrosine residues on thyroglobulin
29
what makes up T3
MIT + DIT
30
what makes up T4
2 x DIT
31
where are T3 and T4 stored and secreted from
colloid thyroglobulin until required
32
how are thyroid hormones transported in the blood
bound to plasma proteins and some free
33
what are the main transporters of thyroid hormones
thyroid binding globulin
thyroid binding prealbumin
albumin (5%)
transthyretin
34
does TBG or TBPA carry more thyroid hormones
TBG (70%) TBPA (20%)
35
how do thyroid hormones cause transcription of genes
bind to receptors in target cells
complex translocation to nucleus
bind to thyroid response elements on target genes
stimulates transcription of genes
36
what is more common T4 or T3
T4 (90%)
37
is T4 or T3 more potent
T3 is 4 times more potent
38
does T4 or T3 bind better
T4 binds better
| T3 bound much less avidly by TBG and not significantly by TTR
39
does T4 or T3 have more rapid onset/offset action
T3
40
what hormone is released from the hypothalamus to start the HPT axis
TRH
41
what hormone is released from the anterior pituitary in response to TRH
TSH
42
what cells release TSH in the anterior pituitary
thyrotroph cells
43
what kind of receptor does TRH act on
GPCR - Gq
44
what kind of receptor does TSH act on to stimulate release of thyroid hormones
the TSH receptor on surface of thyroid epithelial cells is a GPCR
45
what happens when the TSH GPCR is stimulated
GTP --> GDP and cAMP is produced - causes production and secretion of T3 and T4
46
what feedback do the thyroid hormones have on the hypothalamus and pituitary
negative feedback (T4-->T3 which causes -ve feedback)
47
what is the function of deiodinase enzymes
activation/deactivation of thyroid hormones by addition/removal of an iodine atom
48
where is D1 found
liver and kidney
49
where is D2
```
heart
skeletal muscle
CNS
fat
thyroid
pituitary
```
50
where is D3 found
foetal tissue
placenta
brain (not pituitary)
51
what does D1 do
converts T4 to T3
52
what does D2 do
converts T4 to T3
53
what does D3 do
converts T4 to rT3
54
what is it called when the thyroid fails to descend
lingual thyroid
55
where is the thyroid found if it descends excessively
retrosternal location in mediastinum
56
thyroxine is
T4
57
triiodothyronine is
T3
58
what drugs prevent iodine attaching to tyrosine residues on thyroglobulin to form MIT and DIT
carbimazole and propylthiouracel
59
is T3 or T4 the major biologically active molecule
T3
60
where is T4 converted to T3 mainly
liver and kidney
61
what is measured in ninewells with regard to thyroid function
free T3 and free T4
62
what do thyroid hormones do to the BMR
increase BMR
63
what do thyroid hormones do to thermogenesis
increase thermogenesis
64
what do thyroid hormones do to carbohydrate metabolism
increase CHO metabolism
65
what do thyroid hormones do to to lipid metabolism
increase lipid metabolism
66
what do thyroid hormones do to protein synthesis
increase protein synthesis
67
the production and secretion of what requires thyroid hormones
GHRH
68
what hormones require presence of thyroid hormones for activity
GH/somatomedins
69
what part of foetal development/neonatal brain development requires thyroid hormones
myelinogenesis and axonal growth
70
what do thyroid hormones do to responsiveness to adrenaline and noradrenaline and how
increase responsiveness by increasing number of receptors
71
what do thyroid hormones do to to cardiovascular responsiveness
increased rate and force of contraction
72
what do low temperatures in babies and young children do to TRH release
low temperatures stimulate TRH release
73
what does stress do to the release of TRH and TSH
inhibits it
74
when are thyroid hormones highest and lowest
highest late at night and lowest in morning
75
what is the biochemistry of primary hypothyroidism
low fT4/fT3
| high TSH
76
what is the biochemistry of primary hyperthyroidism
high fT4/fT3
| low TSH
77
what is the biochemistry of secondary hypothyroidism
low/normal TSH
| low fT4/fT3
78
what is the biochemistry of secondary hyperthyroidism
high/normal TSH
| high fT4/fT3
79
MCV in primary hypothyroidism
increased
80
CK in primary hypothyroidism
increased
81
LDL cholesterol in primary hypothyroidism
increased
82
Na in primary hypothyroidism
hyponatraemia
83
prolactin in primary hypothyroidism
hyperprolactinaemia
84
ESR, Ca and LFTs in hyperthyroidism
increased
85
what is the main cause of hypothyroidism
Hashimoto's thyroiditis
86
what are some other causes of hypothyroidism
```
iodine deficiency
drug induced - amiodarone, lithium
atrophic thyroiditis
post ablative therapy/post radio therapy
post thyroidectomy
pituitary/hypothalamic pathology
```
87
what 4 autoimmune conditions are commonly seen with hypothyroidism
T1DM, Addisons, pernicious anaemia, vitiligo
88
what can hypothyroidism cause in babies
cretinism - dwarfism and limited mental function
89
what the main symptoms of hypothyroidism
```
lethargy/fatigue
slow pulse
constipation
reduced BMR
weight gain but decreased appetite
coarse/sparse hair
hyperlipidemia
cold intolerance
slow responses
mental sluggishness
obstructive sleep apnoea
cramps
deep hoarse voice
depression
menorrhagia/amenorrhoea/oligomenorrhoea
prolonged tendon jerks
```
90
what are some cardiac effects of hypothyroid
cardiac dilation
worsening heart failure
pericardial effusion
reduced HR
91
what are some GI effects of hypothyroid
intestinal obstruction
megacolon
ascites
92
what nerve problem is seen in hypothyroidism
carpal tunnel
93
other s/s of hypothyroid
```
pale, cool doughy skin
periorbital oedema
pitting oedema
macroglossia
hyperprolactinaemia
reduced memory
cerebellar ataxia
hypercarotenaemia
myalgia
dull/expressionless face
```
94
what is the treatment for hypothyroidism in young patients
50-100 ug levothyroxine (T4) daily
95
what is the treatment for hypothyroidism in elderly or history of IHD
25-50 ug levothyroxine (T4) daily
| adjust every 4 weeks according to response
96
when should thyroxine be taken
before breakfast
97
how much may dosage increase by in pregnancy
by 50%
98
how soon should TSH be checked after a dose change
8 weeks
99
how often should TSH be checked once stabilised
12-18 months
100
is there any benefit of using T3 and T4 combination therapy
no
101
why is T3 rarely used in the treatment of hypothyroidism
effects develop within a few hours and disappear within 24-48 hours of discontinuation
102
in secondary hypothyroidism what should amount of thyroxine be titrated against
free T4 level - TSH unreliable as decreased
103
when is myxoedema coma mostly seen
elderly women with longstanding untreated or unrecognised hypothyroidism
104
what ECG changes are seen in myxoedema coma
```
bradycardia
low voltage complexes
varying degrees of heart block
T wave inversion
QT interval prolonged
```
105
how is myxoedema coma treated
```
ABCDE
passively rewarm
monitor for arrhythmias
monitor urine output, fluid balance, CVP, BG, O2 sats
thyroxine cautiously
```
106
why might you give hydrocortisone in myxoedema coma
10% patients have co-existing adrenal failure
107
what type of respiratory failure does myxoedema coma cause
T2RF
| hypoxia, hypercapnia, resp. acidosis
108
what can mortality be up to in myxoedema coma
60%
109
what is hashimotos thyroiditis
autoimmune destruction of the thyroid gland leading to decreased thyroid hormone production
110
what group is hashimotos thyroiditis most seen in
females
| 45-60
111
what HLA genes is hashimotos thyroiditis associated with
HLA-PR3
| HLA-DR5
112
what antibodies are seen in hashimotos thyroiditis
anti-thyroid peroxidase (anti-TPO)
| anti-thyroglobulin
113
what do anti-TPO and anti-thyroglobulin cause when bound
antibody dependent cell mediated cytotoxicity
114
what is seen microscopically in hashimotos
T cell infiltrate and inflammation
115
describe the cytokine mediated cell death seen in hashimotos
Y-IFN from T cell activation recruits macrophages
116
what is hashitoxicosis
transient hyperfunction preceding hypofunction in hashimotos thyroiditis
117
is hashimotos goitrous
yes - lymphatic and plasma cell infiltrate
118
what are you at increased risk of with hashimotos thyroiditis
other AI disease
| B cell non-hodgkins lymphoma
119
is primary atrophic hypothyroidism goitrous
no
120
what are the main symptoms of hyperthyroidism
```
palpitations
weight loss
heat intolerance
sweating
insomnia
excessively emotional
increased BMR
very fast pulse
nervousness
tremor
irritability
diarrhoea
```
121
what are some other features of hyperthyroidism
```
proptosis
AF
diplopia
muscle weakness (upper arms and thighs)
lid retraction
hair brittle and thin
lighter/less frequent periods
rapid fingernail growth
```
122
what are 4 diseases causing excessive thyroid stimulation and therefore thyrotoxicosis
GRAVES
hashitoxicosis
thyrotropinoma
choriocarcinoma
123
what is a thyrotropinoma
TSH secreting pituitary adenoma
| rare
124
what is a choriocarcinoma
trophoblast tumour secreting hCG
125
what are 2 nodular diseases causing thyrotoxicosis
toxic solitary nodule
| toxic multinodular goitre
126
what is a toxic solitary nodule usually
adenoma
127
where is toxic multinodular goitre seen usually
elderly
| iodine deficient areas
128
what is seen in nodular disease
asymmetrical goitre
129
would nodular disease show high uptake on scintigraphy
yes - high nodular uptake
130
when would toxic multinodular goitre be treated with surgery
symptoms of an enlarged thyroid (dysphagia/dyspnoea)
131
is toxic multinodular goitre antibody positive or negative
negative
132
what are 2 causes of ectopic production causing thyrotoxicosis
metastatic follicular thyroid cancer
| strauma ovarii
133
what is a strauma ovarii
ovarian teratoma with thyroid tissue - mostly benign tumours but can be malignant
134
what are 2 other causes of hypothyroidism
iodine excess
| thyroiditis
135
what is the 1st line antithyroid drug
carbimazole once daily
136
what is 2nd line antithyroid drug
propylthiouracil twice daily
137
which ATD is used in 1st trimester of pregnancy
propylthiouracil
138
what can carbimazole cause in early pregnancy
aplasia cutis
139
does carbimazole or propythiouracil cause more side effects
propythiouracil
140
how do ATDs work
inhibit thyroid peroxidase therefore blocking thyroid hormone synthesis
141
what does propythiouracil also do (aswell as blocking TPO)
inhibits DIO1 so stops T4-->T3
142
what 3 effects can ATDs have on the liver
cholestatic jaundice
increased liver enzymes
fulminant hepatic failure
143
what is the major side effect of ATDs
agranulocytosis
144
what % of people on ATDs get agranulocytosis
< 0.5%
145
when is the highest risk of getting agranulocytosis with ATDs
first 6 weeks
146
what must you say to a patient starting ATDs
written and verbally tell them to stop drug and get urgent blood count in event of fever, oral ulcer or oropharyngeal infection
147
what % of people get an allergic type reaction with ATDs
1-5% - urticarial, rash, arthralgia
148
what drug is used for immediate symptomatic relief in hyperthyroid and why
propranolol
149
how do beta blockers help in hyperthyroid
B-adrenoreceptor blockade, reduced sympathetic activity
| also inhibition of DIO1
150
when are beta blockers contraindicated and what should be used instead
asthmatics
| CCB - diltiazem
151
what is the first line treatment in relapsed Graves and nodular thyroid disease
radioiodine
152
when is radioiodine contraindicated
pregnancy
breast feeding
active TED (can be used with steroid cover)
153
what is there a risk of when radioiodine is used with graves
hypothyroid
154
when is a thyroidectomy useful
when radioiodine is contraindicated
155
what causes graves disease
circulating IgG autoantibodies binding to and activating GPCR of thyrotropin. this causes smooth thyroid enlargement and increased hormone production
156
what antibodies are seen in graves
TSH receptor antibodies (TRAb)
| not specific - thyroid peroxisomes + thyroglobulin
157
what group is graves most likely to occur in
females
| 20-50 yr old
158
what acts as TSH in graves
thyroid stimulating immunoglobulin (TSI) - unchecked by T3 and T4
159
is there goitre in graves
yes - smooth
160
what Ig is seen in graves
IgG
161
what are the TSH and fT3/fT4 levels seen in graves
decreased TSH
| increased fT4/fT3
162
what are the levels of Ca and ALP seen in graves and why
Increased ALP
hypercalcaemia
- due to increased bone turnover and osteoporosis
163
what happens to the WCC in graves
decreased (leuropenia)
| - often mild and not a sign of agranulocytosis
164
what is a definitive diagnosis of graves
raised titre of TRAb
165
what is the triad of features seen in graves
hyperthyroid +
- diffuse enlargement of thyroid
- eye changes
- pretibial myxoedema
166
what is thyroid acropatchy
soft tissue swelling of hands and clubbing of fingers seen in graves
167
what are the eye changes seen in graves
TED
168
is there a thyroid bruit in graves
yes - with large goitres, not heard in other goitrous conditions
169
is TED uni or bilateral
either
170
what is the treatment of mild TED
lubricants
171
what is the treatment of severe TED
steroids, radiotherapy, surgery
172
how is diplopia treated in TED
Fresnal prism
173
what autoimmune conditions is graves assoc. with
vitiligo
addisons
T1DM
174
what is a thyroid storm
medical emergency - severe hyperthyroidism
175
when is a thyroid storm seen
hyperthyroid patients with acute infection/illness/recent thyroid surgery
176
what is seen in a thyroid storm
exaggerated reflexes
respiratory/cardiac collapse
hyperthermia
177
what is the treatment of a thyroid storm
```
ABCDE
lugols iodine
PTU
glucocorticoids
BBs
fluids and monitoring
```
178
what is thyroiditis
inflammation of the thyroid gland
179
what are some causes of thyroiditis
```
autoimmune - graves and hashimotos
infection
de quervains/sub acute (viral)
post partum
radiation
drug induced
acute suppurative thyroiditis (bacterial)
```
180
what are 2 polymorphisms in immune regulation genes assocaited with autoimmune thyroiditis
CTLA-4
| PTPN-22
181
what does CTLA-4 do
negative receptor of T cell responses
182
what does PTPN-22 do
inhibits T cell function
183
what is seen in the free T4/T3 levels in sub-acute thyroiditis
T4 rises then falls then normal
184
what is seen in the TSH levels of sub acute thyroiditis
TSH falls then rises then normal
185
who is sub-acute thyroiditis most likely to occur to
females
20-50 years
following viral infection
186
what kind of goitre is seen in sub-acute thyroiditis
painful goitre with low uptake on scintigraphy
187
what is the treatment of sub-acute thyroiditis
self limiting
| NSAIDs
188
what is the effect of amiodarone on thyroid function
iodine rich drug structurally similar to T4
| can cause hypothyroid due to toxicity from iodine excess or amiodarone induced thyrotoxicosis
189
what is the biochemistry of subclinical hypothyroidism
increased TSH
| normal T4/T3
190
what is the biochemistry of subclinical hyperthyroidism
decreased TSH
| normal T4/T3
191
when is treatment advised in subclinical hypothyroidism
when TSH > 10
192
when is treatment advised in subclinical hyperthyroidism
when TSH < 0.1
| or co-existing osteoporosis/fracture/AF
193
when is sick euthyroid syndrome seen
unwell hospital patients
194
what is seen in sick euthyroid syndrome
TSH typically suppressed initially due to intercurrent illness and then rises during recovery
195
should you check thyroid function in unwell patients
not unless clinical suspicion of thyroid disease
196
why may graves settle in pregnancy
pregnancy suppresses autoimmune disease - post partum there is an exacerbation of AI diseases
197
why may hyperthyroidism occur in pregnancy
hCG increases thyroxine production
198
why may hypothyroidism occur in pregnancy
thyroid under extra demand and may not be able to compensate
199
what is the treatment for hyperthyroid with pregnancy
supportive
BB if needed
low dose antithyroid drugs (PU 1st trimester)
200
what is post partum thyroiditis
previously functioning thyroid gland becomes inflamed within 1st year after child birth - small diffuse non-tender goitre, transiently thyrotoxic then hypothyroid
201
what is a dermoid cyst
rare congenital cyst
202
when would a dermoid cyst usually present
teens
203
how would you describe a dermoid cyst
midline swelling that is soft and non-fluctuant
204
where does a thyroglossal cyst occur
anywhere along thyroglossal tract - midline swelling
205
when would a thyroglossal cyst present
teens
206
where does a brachial cyst occur
upper anterior triangle swelling
207
what is a brachial cyst
persisting 2nd brachial arch
208
when does a brachial cyst present
teens
209
"half filled water bottle"
brachial cyst
210
what is seen on FNA of a brachial cyst
cholesterol crystals
211
where does a cystic hygroma occur
posterior triangle swelling
212
when would a cystic hygroma present
1st year of life
213
how would you describe a cystic hygroma
can be large - can cause pressure symptoms
lymph filled
transilluminate
