Thyroid Flashcards
what levels of the spine correlate to the thyroid?
C5 - T1
what is the additional artery which may supply the thyroid?
thyroid ima
what is the parasympathetic innervation of the thydoid?
vagus
what is the symp innervation of the thyroid?
sup / mid / inferior ganglia of the symp trunk
runs with the s / m / i arteries
describe the follicle
The follicles are lined with follicular cells and are filled with a fluid known as colloid that contains the prohormone thyroglobulin (which is like an attatchment site for different hormones / tyrosine)
there is iodine uptake to follicular cells. what happens next?
iodine attached to tyrosine residues on thyroglobulin to form (MIT) & (DIT). from this, T3 and T4 are formed.
T3 and T4 are stored in the colloid thyroglobulin until needed!
plasma protiens: what % of T3 / T4 binds to…
- albumin?
- thyroxine binding pre-alb?
- thyroxine binding globulin?
5% to albumin
20% to thyroxine binding pre-albumin
70% - most bind to thyroxine binding globulin
5% is free and active, unlike the rest of us xx
what is the effect of thyroid hormones on the sympathetic nervous system?
thyroid hormones lead to an increase in the number of receptors for adrenaline / noradrenaline, so ENHANCES the effect of sympathetic mediators.
How do you treat symptoms caused by the thyroid hormone effect on the sympathetic nervous system?
increased HR and force of contraction (due to more noradrenaline receptors cropping up) can be reversed using PROPANOLOL.
What environmental factor can increase thyroid hormone release in babies?
cold temperatures
does stress inhibit or enhance thyroid hormone release?
inhibits release
2 Delodinase enzymes deactive thyroid hormones. where is
D1?
D3?
d1 - liver and kidneys
d2 - everywhere - heart and skeletal muscle, CNS, fat , thyroid, and pituitary
d3 - fetal tissue, placenta and brain (not pituitary)
what is the mechanism of inactivation of D1 and D3?
T4 –> reverse T3 !!
what does D2 do and where?
D2 activates T4–> T3!!
heart, skeletal muscle, CNS, fat , thyroid, and pituitary
what is the effect on TSH if T3 and T4 are low?
TSH would be high
this doesn’t cause goitre.
what is the autoimmune mechanism of graves?
there is lots of TSI - thyroid stimulating immunoglobulin
this acts in the same way as TSH, and is unregulated by negative feedback with T3/4
joseph’s thyroid hasn’t bothered to descent and you can see it beside his tonsils. what is this called?
a lingual thyroid
what does thyroxine bind to and where? whats the effect?
what - Thyroid response elements
where - target genes all around the body
effect - increased BMR through transcription changes
2 drugs that commonly cause hypothyroidism associated thyroiditis?
amiodarone - v common
also lithium
does de Quervains subacute thyroiditis cause pain?
no
what thyroid condition is predisposed by Turners and Down’s syndrome?
Hashimoto’s hypothyroidism
anti- thyroglobulin and anti - thyroperoxidase (tpo) is high — what could this show?
Hashimoto’s (autoimmune antibodies)
does iodine deficiency cause diffuse or nodular goitre?
both ! ha ha !
treatment of thyroid cancer
- thyroidectomy
- radiotherapy ablation
- thyroid replacement forever
describe the most common thyroid cancer
1 = Papillary (75-85%)
Multi-nodular
Spread via lymph nodes
describe 2nd most common thyroid cancer
2 = Follicular (from thyroid epithelium)
Single Nodule
Haematogenous spread
what thyroid cancer has the worst prognosis?
ANAPLASTIC
Rapidly expanding undifferentiated tumour
Normally mets by diagnosis
Associated with p53
what thyroid cancer arises in parafollicular cells?
Medullary - C cell from parafollicular
Single nodule
Airway compromised
4 month old Jenna has a big swelling behind her left ear that is transilluminate. what is it?
Cystic Hygroma
Benign swelling full of lymph
Occurs in babies < 1
Can cause pressure symptoms
where to branchial cysts occur?
upper anterior triangle of children
failed fusion of 2nd and 3rd branchial arches
what are dermoid cysts?
soft benign teratomas of dermatology structures - soft and can occur in the midline of the neck
what midline neck cyst would move with the tongue?
Thyroglossal cyst
Contain lymph which may get infected
Hypothyroid women need more replacement when they get pregnant (mimic physiological increase) – how do you test that they are getting enough??
test TSH - should be inhibited, so low
should be < 3 Mu / L
recommended dose of thyroxine in hypothyroid woman??
- once you suspect pregnancy
- throughout pregnancy
- up to 25mg - ASAP
- up to 150mg by 20 weeks
what hormone supports egg development / release, and is biochemically similar to thyroxine??
hCG
what can cause hyperthyroidism in weeks 0-20 of pregnancy specifically??
hCG associated hyperthytoidism
treatment of hyperthyroidism in pregnancy (2 drugs, when?)
1st tri = propylthyriouacil
3rd = Carbimazole
what is neonatal transcient hypothyroidism caused by???
TRAbs crossing the placent (thyroid receptors antibodies)
hypothyroidism in pregnancy can be life threatening to the mum and baby – true or false??
TRUE
mum = pre-eclampsia, premature labour, haemorrhage
baby = abortion, low IQ
how could babies “acquire” thyroid disease? (3)
infection
autoimmune disease
iodine deficiency
what 3 things can lead to primary congenital thyroid disease? (in contrast to secondary / tertiary congenital thyroid disease)
Primary = a problem within the thyroid itself
dysplastic thyroid
sublingual thyroid - developed in wrong place
metabolism error
how is congenital thyroid disease in babies picked up??
POSITIVE DAY 5 GUTHRIE TEST - HIGH TSH AND LOW T4
consequence of failing to notice congenital thyroid disease?
cretinism develops by 3 months
classic presentation of a congenital thyroid disease baby? (3)
- delayed jaundice
- constipation
- gaining weight despite poor feeding!!
what is seen on histology of de Quervains subacute thyroiditis?
granulatous inflammation / giant cell
what is seen on histology of Reidel’s subacute thyroiditis?
dense fibrosis
what it the difference between primary and secondary congenital thyroid disease?
primary - a problem within the thyroid eg. metabolism error
secondary - a problem in the thyroid stimulating sequence eg, hypopituitarism
