Hyperthyroidism

Question 1

Explain how Thyroxine and Trioodothyronine is made

Answer 1

In the follicule: TSH binds to TSHR = thyroid peroxidase activation and TG synthesis
Iodide uptake via Na+/I- symporter

Colloid: TG, iodide, migrate here
TPO oxidises iodide = iodine, this iodine binds to TG to form MIT and DIT
MIT and DIT undergo coupling reaction via TPO = TGT4 and T3
Proteolysis allows T4 and T3 to unbind from TG

Question 2

How much thyroxine store do we have? What is its main principle function?

Answer 2

A months worth
Thryoxine increases bmr of all cells

Question 3

What is the effect of thyroxine on the pituitary and hypothalamus?

Answer 3

Pituitary produces less TSH
Hypothalamus produces less TRH

Question 4

What is Graves’ disease?
How does it present?

Answer 4

Autoimmune disease where antibodies bind and stimulate TSH receptor on thyroid causing excess thyroxine production
Symptoms: smooth goitre
Facial flushing
Nervous, irritable
Tachycardia
Hunger
Weight loss
Exopthalmos- antibodies bind to muscles behind the eye
Pretibial myxoedema-antibodies bind to muscles on shin causing growth

Question 5

What is toxic modulate thyroid disease? (Plummers disease)
What presentations of grave’s disease will it not have?

Answer 5

Benign tumour on thyroid that starts to make thyroxine
Will look one sided on scintigram
No pretibial myxoedema
No exopthalmus

Question 6

How does thyroxine affect the sympathetic nervous system?

Answer 6

Sensitises beta adrenoreceptors to ambient levels of adrenaline and noradrenaline
= tachycardia and palpitations and lig lag

Question 7

What is a thyroid storm?

Answer 7

Medical emergency
Hyperpyrexia > 41
Tachycardia
Cardiac failure
Delirium
Jaundice
Only need 2 to be in thyroid storm

Question 8

What are treatment options for hyperthyroidism?
What are the advantages and disadvantages of each?

Answer 8

Thyroidectomy- can damage voice box
Thionamides- Carbimazole and PTU (propothiouracil) block thyroid peroxidase (enzymes)
Can cause neutropenia- must go a&e if you have a sore throat
Takes a while to kick in as we have thyroxine stores
Potassium iodide- makes gland shut down- good for prepping for surgery and thyroid storm
Inhibits iodination of thyroglobulin
Radioiodine- kills overactive thyroid cells and shrinks enlarged thyroid gland, have to avoid pregnant women and children
B-blockers- eg propranolol only therapeutic

Question 9

What is viral thyroiditis? How does it present?

Answer 9

Infection that attacks thyroid gland causing a release in thyroxine
Thyroid stops making thyroxine and makes virus = hypothyroidism
Zero radioiodine uptake = no scintigram
Symptoms: Pyrexia, painful dysphagia,

Question 10

How would you image a thyroid to test for Graves’ disease?

Answer 10

Inject radioactive iodine and perform a thyroid scan
Should show enlarged smooth uniform thyroid