Thyroid Disorders Flashcards
Where are t4/t3 produced?
All of T4 is produced in the thyroid
20% of t3 is secreted, the rest is from peripheral conversion of T4
T3 is active form, vital for growth and development
How is T4 converted to T3 and what happens when this doesnt work?
Monodeiodinisation be deiodinase enzymes (d1-3)
Deficiency in these enzymes causes high TSH, high T4 and low T3
What proteins bind thyroid hormones?
TBG, TBPA, albumin
What tests can you do for thyroid function?
-Serum TSH, freee t3 and free t4
Anti TPO Ab
Anti TSHR ab
USS thyroid to see if lesion is cystic/solid
Radioactive iodine uptake scan (i123)
CXR head and neck (retrosternal goitre, compression)
Serum thyroglobulin- useful in monitorring Ca
What would radionuclide uptake scans show in different causes?
Graves disease shows even uptake
Toxic nodular goitre shows patchy uptake
Thyroiditiss shows reduced uptake
cold nodules have a 20%chance of being malignant
What would TFTs show in sick euthyroid?
everything is low
Where do you see sick euthyroid syndrome?
Starvation states, severe illness requiring ITU, renal failure, cardiac/liver failure
Dont need to give thyroxine
What is struma ovarii?
Ovarian teratoma with hyper functioning thyroid tissue. No thyroid enlargement, decresed uptake on scintigraphy
How does TSH vary in the day?
trough at around 2, can be around 30% higher in darkness. Monitoring should always be done at the same time of day
How is TBG affected by other processes/drugs?
Increased in: Pregnancy, Pill/HRT, hepatitis
Decreased in: nephrotic syndrome, malnutrition, androgens, steroids, chronic liver disease, phenytoin, acromegaly
What would TFTs show in primary hyper thyroidism?
TSH-low, T4- Raised, T3- Raised
What would TFTs show in Subclinical hyperthyroidism?
TSH-low, T4- normal, T3- normal
What would TFTs show in secondary hyperthyroidism?
TSH -high, T4- Raised, T3- Raised
What would TFTs show in primary hypothyroidism?
TSH -high, T4- low, T3- low
What would TFTs show in Subclinical hypothyroidism
TSH -high, T4- normal, T3- normal
Most common causes of thyrotoxicosis?
Graves disease
Toxic nodular goitre
Thyroiditis
Less common causes of hyperthyroid?
tsh secreting adenoma, neonatal, ectopic thyroid tissue, amiodorone
What is the Ab in Graves?
Anti TSHRAB
Signs and symptoms of hyperthyroid?
CVS: tachycardia, AF, SOBOE, ankle swellin, cardiomyopathy
GI: diarrhoea, wt loss, incr appetite
Eyes/skin: sore, gritty, double vision, staring, pruritis
Neuro: tremor, proximal myopathy, anxiety
Other: ht intolerance, sweating, oligo/amennorhea, osteoporosis
what does the goitre feel like in graves?
diffusely enlarged, bossellation, soft and symmetrical. May be a bruit
Eye disease in graves?
Lid lag/retraction conjunctival oedema (chemosis) periorbital puffiness proptosis ophthalmoplegia grittiness exposure keratitis optic neuropathy
assymetrical often, unilateral in 15%
RAPD may show optic nerve compression so get help.
Skin symptoms in graves?
pretibial myxoedema
acropachy
vitiligo?
Who should be screened for thyroid dysfunction?
Those with AF hyperlipidaemia DM T1DM and pregnant amiodoron or lithium downs, turners, addisons disease
Associated conditions with graves?
DM Addisons vitiligo pernicious anaemia alopecia areata MG coeliac
in first trimester what effect on tfts?
use diffferent references as tsh can be low in some women
Main risk factor in eye disease?
Smoking, 25-50%with graves will develop it. May not correlate with thyroid disease
Treatment for thyroid eye disease?
mild: conservative: lift bed etc
Severe: steroids (methylpred) may help. Surgery may be needed if sight threatening
Initial Management of Graves?
Refer all with overt signs to endo
Initially give a B Blocker to ameliorate symptoms
First line is thionamides: CBZ and PTU
compliance is better with CBZ and no chance of liver injury. most are euthyroid 8 weeks after. monitor every 6 weeks
Remission 40% at 18 mo
S/E of thionamides?
liver injury: ptu
agranulocytosis
maculopapular rash
vasculitis
When do you give PTU over CBZ?
pregnant, breast feeding, storm
C/I to radio iodine?
Active orbitopathy, pregnant, breast feeding
stay away from preg and kids for 3 weeks
no babies for 6mo (4 if man)
Risks of Radioiodine?
hypothyroidism, teratogenesis, optimal dose is unpredictable
when is surgery considered?
failed/intolerant to medical therapy, obstructive symptoms, malignancy suspected
complications of surgery?
hypo hypoPTH recurrent laryngeal nerve damage bleeding (v vascular thyroid in graves) storm
How can you prevent bleeding in thyroid surgery?
give lugols iodine, wolff chaikoff effect. large amounts of iodine reduces hormone
S+S of storm?
N+V confusion agitation acute abdo, cvs collaps, heart failre, incr. temp tachy AF
Precipitants of storm?
recent surgery/Radioiodine
infection
mi
trauma
Management of storm?
iv saline
take bloods for TFT
Sedate if needed
Propanolol, digoxin if need to slow heart
carbimazole/ptu. lugols after 4 hours
steroids
abx for infection
Causes of hypothyroidism?
1o: iatrogenic: amiodorone, lithium, surgery/R/I
AI: hashimotos, de quiervans, atrophic
2o: pituitary/hypothalamus tumours, trauma to either
symptoms of hypothyroidism?
tired, lethargic, mood down, cold intolerant, wt gain, constipation, hoarse voise, decreased memory/cognition, dementia, cramps, weakness
Signs of hypothyroidism?
Bradycardic B Reflexes slow Aataxia (cerebellar) Dry hair/skin Yawingin (tired) Cold intolerance Ascites +non pitting oedema Round face Defeated demeanor Immobile, ileus CCF
Causes of AI hypothyroidism?
primary atrophic: lymphcytic infiltration, no goitre as atrophy
hashimotos: women 60-70, auto antibody titres high
problems in pregnancy with hypothyroidism?
eclampsia, anaemia, prematurity, low BW, still birth
Treatment for hypothyroidism?
Levothyroxine, 50-100ug
review at 12 weeks, adjust 6 weekly by clinical state but not to suppress TSH
Changes to treatment in elderly with hypothyroidism?
reduce dose to 25, increase carefully as may precipitate angina/mi
why is amiodorone a bugger in thyroids?
iodine rich, 2% get problems. hypo can be caused by toxic iodine excess, thyrotoxicosis from destructive thyroiditis that causes release. half like 80 days so problems persist
Myxoedema Coma signs
looks hypop old hypothermia low BG bradycardia coma seizures
may have had recent iodine/surgery. cyanotic, low bp and HF
management of Myxoedema Coma?
bloods oxygen if cyanosed
correct hypoglycaemia
T£ IV slowly
hydrocortisone
iv saline
abx if infection
what can affect absorption of LT4?
Gi conditions: ibd, coeliac, gastritis
milk and coffee
Important flags for thyroid cancer?
solitary/multinodular lump, clinically euthyroid
FH LN swellin Hoarseness/change in voice Difficulty swallowing stridor
RF for thyroid cancer?
radiation exposure, neck irradiation
types of thyroid cancer?
paipillary
follicular
anaplastic
medullary
why give steroids in thyrotoxic storm?
prevents peripheral conversion of t4 to t3
