Hyperthyroidism Flashcards
what is thyrotoxicosis?
the clinical manifestation of excess thyroid hormone action at the tissue level due to inappropriately high circulating thyroid hormone concentrations
what is hyperthyroidism?
a subset of thyrotoxicosis, referring specifically to excess thyroid hormone synthesis and secretion by the thyroid gland
where is the thyroid gland located within the neck in relation to the vertebrae?
C5-T1
what are the causes of thyrotoxicosis?
- graves’ disease
- toxic multinodular goitre (TMG)
- iodine excess
- iatrogenic (e.g. amiodarone, levothyroxine)
- viral (e.g. subacute De Quervain’s thyroiditis)
- postpartum thyroiditis
what is graves’ disease?
- an autoimmune condition mediated via anti-TSH-receptor (anti-TSHR) autoantibodies, which bind to TSH-receptors on the thyroid gland and stimulate increased production of T3 and T4 from the thyroid gland, resulting in thyrotoxicosis
- thyroxine receptors in the pituitary gland are activated by the excess hormone, resulting in the suppression of TSH release due to negative feedback
what is toxic multinodular goitre (TMN)?
- caused by the development of physiologically active nodules on the thyroid gland, which are capable of secreting thyroid hormones
- these nodules are not responsive to circulating TSH concentrations and so, eventually cause thyrotoxicosis
what is subacute De Quervain’s thyroiditis?
- a transient rise in thyroid hormone production due to inflammation of the thyroid gland and subsequent excessive excretion of thyroid hormones into the circulation
- presents with a painful lump in the neck
- patients may subsequently develop hypothyroidism if the thyroid gland tissue is damaged by the inflammation
what is postpartum thyroiditis?
- presents with a transient acute phase of thyrotoxicosis, followed by a period of hypothyroidism
- can occur 2 – 6 months following birth or miscarriage
what are the symptoms of thyrotoxicosis?
- weight loss
- increased appetite
- diarrhoea
- heat intolerance
- over-activity/restlessness
- tremor
- palpitations
- irritability
- weakness
- loss of libido
- oligomenorrhoea
what are the signs of thyrotoxicosis on examination?
- thin, brittle hair
- warm, moist skin
- irregular, fast HR
- fine tremor
- brisk reflexes
- palmar erythema
- lid lag
- lid retraction
- goitre
what are the signs on examination of graves’ disease?
- thyroid eye disease (e.g. conjunctival injection, aching at the back of the eye, diplopia, gradual proptosis (exophthalmos), lid retraction, lid lag, chemosis (oedema of the eye))
- thyroid acropachy (e.g. clubbing or swelling of the digits)
- pretibial myxoedema
what are the investigations for thyrotoxicosis?
- TFTs
- autoantibody (e.g. anti-TSHR, anti-TPO, anti-Tg)
- US
what is the management of thyrotoxicosis?
- beta-blockers (e.g. propranolol)
- ‘block & replace’ (e.g. carbimazole, levothyroxine)
- ? radioiodine
- thyroidectomy
what are the long-term complications of thyrotoxicosis?
- ‘thyroid storm’
- cardiac (e.g. AF, HF, angina)
- graves’ ophthalmopathy
what is a ‘thyroid storm’?
a serious complication of thyrotoxicosis is the onset of a thyroid storm, which involves excessive adrenergic activity secondary to thyrotoxicosis
- palpitations
- tachycardia
- tremor
- nausea
- vomiting
- abdominal pain
- reduced level of consciousness
- confusion
- agitation
- seizure
