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.