Hyperthyroidism Flashcards
What does TSH do?
Activates uptake of iodine into the thyroid follicular cell which eventually leads to formation of thyroxine
Activates proteolytic enzyme
How much thyroxine do we store?
Enough for one month
What enzyme allows release of thyroxine from the thyroid follicular cell? How does it do this?
Proteolytic enzyme- makes a hole in the cell
How does the negative feedback loop for thyroxine work?
T3 and T4 have negative feedback on the pituitary AND on the hypothalamus
What will TSH levels be in someone with primary hypothyroidism where the thyroid gland is destroyed?
High TSH
What does thyroxine do?
Increases a lot of metabolic processes
What is Graves disease?
An autoimmune condition where antibodies bind to and stimulate the TSH receptor in the thyroid causing a smooth goitre and hyperthyroidism
What happens to the thyroid in Graves disease?
Smooth goitre
How does Graves disease present?
CNS: Nervousness, excitability, restlessness, emotional instability, insomnia Exophthalmos Sweatiness Mostly female and young Weight loss with increased appetite High pulse Oligo/amenorrhea Swollen ankles and shins (pretibial myxoedema) Tremor Diarrhoea
What is Plummer’s disease? What type of condition is it? How does it differ from Grave’s symptomatically?
Benign toxic nodular goitre of thyroid (NOT autoimmune) that causes hyperthyroidism
NO pre-tibial myxoedema or exophthalmos
What are TSH, T3, T4 levels in someone with Plummer’s?
High T3 and T4
No TSH
How do we differentiate Plummer’s vs Grave’s?
In Plummer’s theres one large benign growth and the rest of the thyroid shrinks
In Graves the whole gland is enlarged
What is any non Grave’s hyperthyroidism classified as?
Plummer’s
aka toxic multi-nodular goitre or hot nodule
How does thyroxine effect the sympathetic nervous system? How does this present?
T3 makes beta receptors more sensitive to adrenaline /noradrenaline (doesn’t bind but makes downstream cascade faster).
This leads to sympathetic activation
Tachycardia, palpitations, tremor in hands (beta receptors in skeletal muscles), lid lag
What is lid lag and how do you test it?
Ask them to follow your finger take it really high up, to mid level and low down and if they have hyperthyroidism their eyelids will lag and stay up slightly too long due to excess adrenaline
What symptoms do you need to ask about when you suspect hyperthyroidism
Weight loss despite increased appetite Breathlessness Palpitations,tachycardia Sweating Heat intolerance Diarrhoea Lid lag and other sympathetic features
What is thyroid storm?
Medical emergency- 50% mortality untreated
Untreated hyperthyroidism= lots of excess thyroxine
What is treatment for a thyroid storm?
Urgent in hospital treatment
What are options for treating hyperthyroidism?
Surgery (thyroidectomy)
Radioiodine
Drugs
What drugs can be used for hyperthyroidism?
Thionamides- propylthiouracil and carbimazole
Potassium iodide
Radioiodine
Beta blockers (only helps with symptoms -fast acting)
How do thionamides work?
Inhibit thyroid peroxidase so reduce T3/T4 synthesis- takes weeks to show on blood test, so give beta blockers for first few weeks
What are side effects of thionamides?
Agranulocytosis- reduction of neutrophils (get sore throats)- reversible on withdrawal of drug
Rashes
When is iodine used to treat hyperthyroidism?
Preparing them for surgery (quick action)
If in a thyroid storm
Why is iodine not an ideal drug?
Its not for long term- only used for 10 days
