Hyperthyroidism & Thyroid disorders Flashcards
what is graves disease
autoimmune cause of hyperthyroidism
what are the symptoms of hyperthyroidism specific to graves disease?
smooth, diffuse goitre
exophthalmos
pretibial myxoedema
what are the generalised symptoms of hyperthyroidism?
weight loss despite increased appetite diarrhoea heat intolerance tachycardia lid lag breathlessness tremors sweatiness
what is the mechanism of graves disease?
anti-TSH receptor antibodies bind to and stimulate TSH receptors
stimulates release of TSH
how does exophthalmos occur in graves?
the antibodies bind to muscles behind the eye
how does pretibial myxoedema occur in graves?
soft tissue growth occurs due to antibody binding
how does graves disease appear on a radioiodine uptake test?
defined black thryoid - pyramidal lobe may be visible
what is plummers disease/toxic nodular goitre?
a benign adenoma of the thyroid, overactive at making thyroxine
normal thryoid cells atrophy
how does toxic nodular goitre appear on a radioactive iodine uptake test?
less uniform uptake - hot nodules
not fully black
atrophy of rest of gland
how does excess thyroxine affect the sympathetic NS?
sensitises b-adrenoreceptors to ambient levels of adrenaline
how does excess thyroxine stimulating the sympathetic NS present?
tachycardia, palpitations, tremors, lid lag
what is thyroid storm?
hyperpyrexia >41c accelerated tachycardia/arrhythmia >170bpm cardiac failure delirium/frank psychosis hepatocellular dysfunction/jaundice
what are the main treatment options for hyperthyroidism?
surgery - thyroidectomy
radioiodine
thionamides (propylthiouracil or carbimazole)
non-specific beta blockers to manage symptoms
what should be done in preparation for thyroidectomy?
potassium iodide for 10 days maximum
beta blockers to relieve symptoms
how do thionamides reduce thyroxine synthesis?
inhibit thyroid peroxidase and hence T3/4 synthesis
biochemical effect - hours but clinical effect - weeks
what are the most concerning side effects of thionamides?
agranulocytosis - rare but reversible upon withdrawal
what is the most common side effect of thionamides?
rashes
is thyroid treatment lifelong?
no - usually stopped after 18 months
patients reviewed annually
what is the mechanism of potassium iodide?
short term wolff-chaikoff effect
inhibits thryoperoxidase + H2O2 generation
also inhibits iodination of thyroglobulin
how long does KI take to have effect on the thyroid?
symptoms reduce within 1-2 days
vascularity and size of gland reduce within 10-14 days
what are the risks of thyroidectomy?
risk of voice change (recurrent laryngeal nerve)
risk of losing parathyroid glands
scar
anaesthetic
how does radioiodine treat hyperthyroidism?
capsule containing 370MBq of I131
destroys the thyroid gland
how does viral thyroiditis differ in presentation?
painful dysphagia
pyrexia
painful upon palpitation
what is the mechanism of disease for viral thyroiditis?
virus attacks thyroid gland
thyroid stops producing thyroxine but stores are depleted (takes ~4wks) then patient becomes hypothyroidic then after 3 months it slowly resolves
free T4 increases, TSH drops
what does viral thyroiditis present similarly to?
post-partum thyroiditis but no pain
when to prescribe beta blockers
to reduce immediate symptoms
whilst waiting for surgery or other medications to work
what beta blocker is given to someone with hyperthyroidism
propanolol
