Hyperthyroidism Flashcards
Draw the control of thyroid activity
What is Grave’s disease?
Autoimmune
Antibodies bind to and stimulate the TSH receptor in the thyroid
Cause goitre (smooth) and hyperthyroidism
What are the symptoms of Grave’s disease?
What is Exophthalmos?
Other antibodies bind to muscles behind the eye and cause exophthalmos
What is pretibial myxoedema (hypertrophy)
The swelling (non-pitting) that occurs on the shins of patients with Graves’ disease: growth of soft tissue.
Not to be confused with myxoedema=hypothyroidism
What happens to the goitre in Grave’s disease?
Diffuse goitre of moderate size and uniform radioiodine uptake
Diffuse enlargement and engorgement of thyroid gland (broken line indicates normal size of gland)
What is Plummer’s disease
Toxic nodular goitre
NOT autoimmune
Benign adenoma that is overactive at making thyroxine.
NO pretibial myxoedema
NO exophthalmos
What are the effects of thyroxine on the sympathetic nervous system
Sensitises beta adrenoceptors to ambient levels of adrenaline and noradrenaline.
Thus there is apparent sympathetic activation
Tachycardia, palpitations, tremor in hands, lid lag
What are the symptoms of hyperthyroidism?
Weight loss despite increased appetite
Breathlessness,
palpitations, tachycardia
Sweating
Heat intolerance
Diarrhoea
Lid lag and other sympathetic features
What is thyroid storm?
Hyperpyrexia > 41oC
accelerated tachycardia / arrhythmia
cardiac failure
delirium / frank psychosis
hepatocellular dysfunction; jaundice
Any 2 confirm thyroid storm
Blood results confirm hyperthyroidism
Needs aggressive treatment
How can you treat thyroid storm?
Surgery (thyroidectomy)
Radioiodine
Drugs
What are the classes of drugs used in the treatment of hyperthyroidism
- The thionamides (thiourylenes; anti-thyroid drugs)
- propylthiouracil (PTU)
- carbimazole (CBZ) - Potassium Iodide
- Radioiodine
- β-blockers
First 3 drugs reduce thyroid hormone synthesis
B blockers help with symptoms
How do thionamides work?
It inhibits thyroid peroxidase (enzyme that makes thyroxine) and hence T3/4 synthesis and secretion
Biochemical effect - hours
Clinical effect - week
Treatment may include propranolol - rapidly reduces tremor, tachycardia
What are the side effect of thionamides ?
Agranulocytosis (usually reduction in neutrophils) - rare and reversible on withdrawal of drug.
Rashes (relatively common)
What does the follow up of hyperthyroidism involve?
Usually aim to stop anti-thyroid drug treatment after 18 months
Review patient periodically including thyroid function tests for remission/relapse
What is the role of b blockers in thyrotoxicosis?
Several weeks for ATDs to have clinical effects eg reduced tremor, slower heart rate, less anxiety
NON-selective (ie b1 & b2) b blocker
eg propranolol
achieves these effects in the interim
What is the purpose of Potassium Iodide?
Preparation of hyperthyroid patients for surgery
Used for severe thyrotoxic crisis (thyroid storm)
What are the problems with surgery for hyperthyroidism?
Risk of voice change
Risk of also losing parathyroid glands
Scar
Anaesthetic
How does radioiodine work?
Swallow a capsule containing about 370 MBq (10 mCi) of the isotope I (131)
Contraindicated in pregnancy
Need to avoid children and pregnant mums for a few days
For scans only (not treatment), 99-Tc pertechnetate is an option.
What does Viral (de Quervain’s) thyroiditis involve?
Painful dysphagia
Hyperthyroidism
Pyrexia
Thyroid inflammation
Summarise the treatment options for hyperthyroidism
Drugs:
-Beta blockade is VERY IMPORTANT
-propranolol
Anti thyroid drugs :
-Carbimazole
-Propylthiouracil
Radioiodine
Surgery (partial thyroidectomy)
How does Viral (de Quervain’s) thyroiditis work?
Virus attacks thyroid gland causing pain and tenderness
Thyroid stops making thyroxine and makes viruses instead
Thus no iodine uptake (ZERO)
Radioiodine uptake zero
Stored thyroxine released
Thus toxic with zero uptake
Four weeks later, stored thyroxine exhausted, so hypothyroid.
After a further month, resolution occurs (like in all viral diseases).
Patient then becomes euthyroid again.
Viral (de Quervain’s) thyroiditis
What happens when virus attacks thyroid gland?
What happens when FT4 slowly falls…
