hyperthyroidism Flashcards
Give two causes of hyperthyroidism?
Graves’ disease, Plummer’s disease.
Outline the pathology of Graves’ disease.
Autoimmune condiiton.
Antibodies bind to and stimulate thyroid TSH receptor.
Causes goitre (smooth) and hyperthyroidism.
Lid lag.
Give some symptoms of hyperthyroidism.
Perspiration.
Muscle wasting.
SOB.
Rapid pulse.
Weight loss.
Moist palms.
Localsed myoxedema.
Exopthalmos.
Goiter.
Palpitations/tachycardia.
Tremor
Increased appetite.
Diarrhea.
Clubbing of fingers.
What is Graves’ exophthalmos?
Protusion of eyes due to growth of soft tissue behind eyes (another antibody).
What is pretibial myxoedema?
Swelling on shins of Graves’ patients - growth of soft tissue (another hormone).
Why does the thyoid grow in Graves’ disease?
Antibodies bind to TSH receptors - they work harder and grow.
How can Graves’ disease be distinguished from other hyperthyroidism forms?
Measure antibody.
Radioactive iodine scan.
Feel their neck.
What causes Plummer’s disease?
Begign overactive adenoma in thyroid making thyroxine.
How does Plummer’s disease differ from Graves’ disease?
Not autoimmune.
Nodular not smooth goitre.
No pretibial myxoedema.
No exopthalmos.
How does the thyroid appear in Plummer’s disease?
Thyroid shrinks due to low TSH (negative feedback due to high Thyroxine) - except for adenoma.
What does a radioactive iodine scan of Plummer’s yield?
A hot nodule - small area of highly active thyroid cells.
what are the effects of thyroxine on the sympathetic nervous system?
Sensitises B adrenoceptors to ambient levels of NA and A.
–> apparent sympatheticv activation.
–> Tachycardia, palpitations, tremor in hands, lid lag.
What is a thyroid storm? Why is it concerning?
The consequences of very high levels of thyroxine. Mismanagement can lead to death.
What are the features of a thyroid storm?
- Hyperpyrexia > 41oC
- accelerated tachycardia / arrhythmia
- cardiac failure
- delirium / frank psychosis
- hepatocellular dysfunction; jaundice
High thyroxine and 2 of these features = thyroid storm.
What are the treatment options for a thyroid storm?
Surgery (thyroidectomy)
Radioiodine
Drugs.
What are the classes of drugs used in hyperthyroidism treatment?
- thionamides (thiourylenes; anti-thyroid drugs)
- propylthiouracil (PTU)
- carbimazole (CBZ) - Potassium iodide
- radioiodine.
- Beta blockers.
How are Beta blockers different to other hyperthyroidism drugs?
They don’t reduce thyroxine, they help with symptoms.
Why might thioamines be used?
- daily treatment of hyperthyroid conditions.
- treatment prior to surgery
- reduction of symptoms while waiting for radioiodine to take effect.
How do thioamides work?
inhibition of thyroid peroxidase and hence T3/4 synthesis and secretion.
Why don’t thioamides not have a clinical effect for a long period of time?
Although biochemical effect in inhibiting synthesis and secretion is quick (hours), lots of thyroxine in colloid and blood (T4 half life = 6 days) which must be used up.
Why might propanolol be included in a treatment regimen of thioamide?
Treat symptoms, e.g. reducing tremor and tachycardia while waiting for thioamide to take effect.
What other 2 mechanisms of action do thioamides have?
Suppress antibody production of Graves’ disease.
Reduce conversion of T4 –> T3 in peripheral tissues (PTU).
What are the potential side effects of thioamides?
Agranulocytosis (neutrophil reduction) - rare, reversible with drug withdrawal.
Rashes - common.
How are thionamides administered?
Orally. Tablets.
