hyperthyroidism Flashcards
What thyroid hormones are made by each part of the axis?
Hypothalamus makes TRH, goes to anterior pituitary to make TSH, TSH binds on TSH receptors on thyroid to make T3 & T4.
What happens in grave’s disease? What are the presenting signs and things it causes and why?
Autoimmune disorders where antibodies bind and stimulate TSH receptor on the thyroid causing increase in thyroid hormone production. Causes diffuse smooth goitre, with uniform radioiodine uptake and hyperthryoidism. Symptoms –> diffuse smooth goitre, warm, increase in BMR, muscle wasting, weight loss, exopthalamus (because antibodies bind to muscles behind the eye) & pretibial myxoedema (swelling non-pitting in shins caused by other antibodies)
What happens in plummer’s disease? What are the presenting signs and differences with grave’s disease?
In plummer’s disease one cell becomes adenomatous (benign tumour), overgrows and is overactive, making more thyroxine. Toxic nodular goitre - presents with lump on one side. Not autoimmune so no antibodies. No exopthalamus or pretibial myxoedema. Radioiodine uptake scan is not as active and is one-sided.
What are the effects of thyroxine on the sympathetic nervous system?
sensitises beta-adrenoceptors to ambient levels of adrenaline & noradrenaline therefore causing effects of too much adrenaline -> tachycardia, sweating, palpitations, heart rate increase, tremor in legs, lid lag. (Sympathetic activation )
What are symptoms of hyperthyroidism?
Sweating, high BMR, weight loss despite high appetite, breathlessness, palpitations, tachycardia, heat intolerance, diarrhoea, lid lag
What is a thyroid storm and what is needed to treat it
Medical emergency where patient with hyperthyroidism + 2 or more of the below: hyperpyrexia > 41, accelerated tachycardia/arrythmia, heart failure, delirium/psychosis, hepatocellular dysfunction, jaundice. Aggressive treatment needed.
What is surgery of thyroid gland called and what are the risks associated with it?
Thyroidectomy. Risks include voice changes because recurrent laryngeal nerve is close, loss of parathyroid glands, scar, anaesthetic.
How does radioiodine help with treatment of hyperthyroidism?
Radioiodine taken up by the thyroid and destroys cells reducing the amount of thyroxine made as well as the size of the gland
What are examples of thionamides and how do they work? How long do they take to work?
Examples include propylthiouracil (PTU) and carbimazole (CBZ). They are used as daily treatment of hyperthyroidism. They inhibit thyroid peroxidase and therefore T3/4 production & secretion. They take 4-6 weeks to work.
When is potassium iodide (KI) used? How does it work? How long for symptoms to reduce? How long should it be used for and why?
Potassium iodide is used to prepare for surgery in order to shrink the gland. Or used in case of thyroid storm. It causes inhibition of thyroid hormone synthesis & secretion (wolff-chaikoff effect) by inhibiting iodination of thyroglobulin (TG) and hydrogen peroxide + thyoperoxidase. The hyperthyroid symptoms reduce in 1-2 days, and vascularity & size of gland in 10-15 days. Drug must be stopped after 10 days. Good for surgery because makes gland smaller and less vascular.
What does radioiodine do and when is it not used?
Radioiodine taken up by the thyroid and destroys cells reducing the amount of thyroxine made as well as the size of the gland. swallow capsule - contraindicated in pregnancy and must avoid kids & pregnant moms for 10 days (isolation)
What do beta-blockers do? What is an example? When are they used for hyperthyroidism?
Beta blockers (eg propranolol) are non-selective beta blockers (b1 & 2) that reduce the effect of adrenaline and therefore reduce tachycardia and tremor quickly. used for quick symptomatic relief in hyperthyroidism
What happens in viral (de Quervain’s) thyroiditis? What are the symptoms? What is seen on radiodine uptake scan and why?
the virus attacks the thyroid gland causing release of endogenous thyroxine and stopping the synthesis of thyroid hormones in order to make more of the virus instead. Therefore this initially causes hyperthyroidism which presents with pain, painful dysphagia, sudden hyperthyroidism, fever and inflammation. The radioiodone uptake scan shows nothing because no iodine is taken up by the gland. 4 weeks later the stored thyroxine is depleted and the patient becomes hypothyroid. After another month this resolves.
What happens in post-partum thyroiditis?
Similar to viral thyroiditis but without the pain and it occurs after pregnancy
