Endo 5 - Hyperthyroid Disorders Flashcards
(48 cards)
State two common causes of hyperthyroidism?
- Grave’s Disease
2. Plummer’s Disease
What type of disease is Grave’’s disease?
Autoimmune
Describe the mechanism of Grave’s disease?
an autoimmune antibody which behaves like TSH and binds to the TSH receptor thus stimulating thyroid hormone production
What does the thyroid gland look like in Grave’s disease on a scan?
The thyroid gland is smoothly enlarged and the whole gland is active
What are some of the signs and symptoms in Grave’s disease?
- rapid pulse
- warm
- localised pretibial myxoedema
- exopthalmos
- excitability/nervousness
- loss of weight
- oligomenorrhoea/ amenorrhoea
What are the two defining features of Grave’s disease?
- Localised pretibial myxoedema
2. Exopthalmos
Explain how pretibial myxoedema happens in Grave’s?
antibody mediated
non-pitting
What causes the exopthalmos?
another antibody, binds to muscles behind eye
What causes Plummer’s disease?
Benign adenoma in the thyroid gland
What would an iodine scan show in a patient with Plummer’s disease?
all the iodine will be taken up by the overactive tumourous part of the thyroid, so you see a hot nodule appear
the rest of the thyroid will not be seen as TSH is 0 so is not being stimulated
How does Plummer’s differ from Grave’s?
not autoimmune
so no pretibial myxoedema and no exopthalmos
Describe the effects of thyroxine on the sympathetic nervous system?
it sensitises beta adrenoceptors to basal levels of adrenaline and noradrenaline
So excess thyroxine causes…
symptoms of having high adrenaline
What causes lid lag?
High adrenaline
What is a thyroid storm?
medical emergency, a rare complication of hyperthyroidism
What are the features of a thyroid storm?
- hyperpyrexia
- accelerated tachycardia
- cardiac failure
- delirium
- hepatic failure
What are the 4 treatments of hyperthyroidism?
- Thionamides
- Potassium iodide
- radioiodine
- beta blockers
Outline the physiology of iodine in the thyroid?
- iodine taken up by the follicular cells
- thyroperoxidase allows for iodination of tyrosine residues
- allows for coupling of t1 and t2 to form t3 and t4
Describe the synthesis of thyroxine by follicular cells
- thyroglobulin is a protein produced by follicular cells
- iodine taken up by the follicular cells
- thyroid peroxidase iodinates tyrosyl residues on the thyroglobulin to form t1 and t2 in the presence of hydrogen peroxide
What is the mechanism of action of thionamides?
- inhibit thyroperoxidase so t3/t4 cannot be made
- reduced synthesis of thyroxine hromones
Why do thionamides take around 2 weeks for their effects to be felt?
stores of thyroxine last 2 weeks + long half life
What two diseases can thionamides be used to treat?
Plummer’s and Grave’s
When do you use thionamide in a patient?
Use it before a thyroidectomy to stabilise the patient
Why do you need to stabilise the patient before surgery?
cannot give anaesthesia to a hypertensive and tachycardiac patient
