Hyperthyroidism Flashcards
What is an autoimmune condition that causes hyperthyroidism?
Graves’ Disease
How does Grave’s disease cause hyperthyroidism?
Antibodies bind to and stimulate TSH receptors, cause an overproduction of thyroxine
What is the physical presentation of Grave’s disease?
Smooth diffuse goitre (not tender to touch) including thrill and bruit (hear blood rush), exophthalmos, pretibial myxoedema
increased BMR, body is overactive
How does exophthalmos work?
Antibodies bind to muscles behind the eye, causing eye to protrude forward
How does pretibial myxoedema work?
Antibodies bind to muscles in shin, causing growth of soft tissue
What is the difference between pretibial myxoedema and myxoedema?
Pretibial myxoedema is a sign of hyperthyroidism, myxoedema is an old name for hypothyroidism
How would you image a thyroid to test for Graves’ disease?
Inject radioactive iodine and perform a thyroid scan - should see a uniform smooth uptake of radioactive material to show an enlarged thyroid scan
How many antibodies associated with hyperthyroidism
3
- attached to thyroid gland (goitre)
- attached to eye muscles (exophthalmos)
- attached to shins (pretibial myxoedema)
What is a cancerous condition that causes hyperthyroidism? (benign)
Plummer’s Disease (aka toxic nodular thyroid disease)
How does this disease cause its effects?
Nodule growths (benign adenomas) overproducing thyroxine
Toxic nodular thyroid disease
Toxic nodular goitre,
no exophthalmos,
no pretibial myxoedema
Not an autoimmune disease
How does the shape of the thyroid gland change with toxic nodular goitre and what effect does this have on TSH&T4?
As one side grows (hypertrophy), the other side of the thyroid gland undergoes atrophy. This means a roughly standard amount of TSH&T4 will be released
What are the key features of a thyroid scan in toxic nodular thyroid disease?
A hot spot - one side will take up radioactive iodine, whereas the other side will not (atrophy) and hence will not show up on the scan.
How does thyroxine affect the sympathetic nervous system?
Thyroxine sensitises beta adrenoreceptors to adrenaline and noradrenaline - and has some sympathetic activation.
Therefore, what are some of the sympathetic effects found in hyperthyroidism?
Tachycardia, palpitations, sweating, tremor, lid lag (eye lid delayed in closing because of some sympathetic innervation)
What are the general symptoms of hyperthyroidism?
Weight loss, appetite increase, tiredness, heat intolerance, diarrhoea
What is a thyroid storm?
(thyrotoxic crisis)
When someone with a thyroid condition does not know about it and ignores it for a long time
What heart condition can a thyroid storm lead to?
atrial fibrillation
If a thyroid storm continues to be undetected, what is the percentage of mortality and what are the two main causes of mortality?
50% mortality, either profound hypotension (think tachycardia) or ventricular fibrillation
What are 5 symptoms of a thyroid storm?
requires aggressive treatment
Hyperpyrexia (>41C),
arrhythmia,
cardiac failure,
jaundice,
delirium
What are the 3 treatment types for hyperthyroidism?
Drugs, Radioiodine, Surgery (thyroidectomy)
What are the 4 classes of drugs for hyperthyroidism?
Thionamides, inhibit enzyme sof the thyroid gland
Potassium Iodide, causes negative feedback within thyroid gland (short term)
Radioiodine (capsule)
Non-selective Beta Blockers
Which drugs are anti-thyroid and which are symptom alleviators?
Non-selective beta blockers are symptom alleviators, thionamides/radioiodine/potassium iodide are anti-thyroid
What are two types of thionamides?
Carbimazole,
PTU (propylthiouracil)
What is the mechanism of action for thionamides?
Inhibit thyroid peroxidase and synthesis of T3/T4
takes a long time to work due to the months store of thyroxine
What are the unwanted actions of thionamides?
agranulocytosis (low white blood cell count),
rashes
What should be done if the more severe adverse effect occurs?
If agranulocytosis occurs, withdraw drug immediately
How long do patients stay on drug treatment for?
18 months, then review periodically
What symptomatic effects do beta blockers have?
Reduced tremors, slower heart rate, less anxiety
What is an example of a non-selective beta blocker?
Propanolol
suppresses both B1 and B2
When is potassium iodide typically used?
Severe thyrotoxic crisis and preparation for surgery
What is the mechanism of action for potassium iodide?
Wolff-Chaikoff effect.
Inhibits iodination of thyroglobulin and prevents peroxide production
Why would you give potassium iodide before surgery?
reduces in size, becomes firmer and does not bleed as easily
What are two risks associated with surgery?
hoarse voice (damage to recurrent laryngeal nerve), parathyroid damage (leading to hypocalcaemia)
What is a precaution people taking radioiodine should take? (best treatment)
Stay at home, avoid seeing pregnant women or children (particularly susceptible to radiation)
What is viral thyroiditis and how does it work?
- A viral infection (de Queraave’s) which attacks thyroid gland, releasing all stored thyroxine using the follicular cells to make viral components instead of more thyroxine
- free T4 rises, TSH drops causing 1 month of hyperthyroidism with no new thyroxine
- fT4 drops, TSH rises causing 1 month of hypothyroidism
- resolution in 2-4 months
What are specific symptoms patients report with viral thyroiditis?
Painful dysphagia (swallowing),
hyperthyroidism,
thyroid inflammation
pyrexia
How do thyroxine levels change in viral thyroiditis?
Initially huge increase (all stored thyroxine is released), then a drop in the levels of thyroxine (as it is not being made), and then eventually stabilises
How do TSH levels change in viral thyroiditis?
Initially a drop (as all stored thyroxine is released), and then an increase (when thyroxine isn’t being made), and then stabilises
How will viral thyroiditis appear in a thyroid scan?
It will not - too occupied making viral components that it does not take in radioactive iodine
What is another type of thyroiditis and when does it occur?
Post-partum thyroiditis after pregnancy
