Thyroid Disease Flashcards
describe the hypothalamus-pituitary-thyroid axis
hypothalamus secretes TRH
TRH stimulates anterior pituitary to release TSH
TSH acts on thyroid to release thyroxine (T4) and triiodothyronine (T3)
T3 + T4 act on body organs
what is primary hypothyroidism
problem with the thyroid gland itself causing it to be underactive e.g autoimmune disease
what is secondary hypothyroidism
problem with the pituitary gland
symptoms of hypothyroidism
bradycardia fatigue cold intolerance constipation weight gain menorrhagia dry hair, pale skin
thyroid function tests primary hypothyroidism
High TSH
Low T3/T4
thyroid function tests secondary hypothyroidism
Low TSH
Low T3/T4
most common cause of hypothyroidism in the developed world
Hashimotos thyroiditis
primary hypothyroidism
what is Hashimotos thyroiditis
autoimmune hypothyroidism
- associated with other autoimmune conditions: T1DM, pernicious anaemia, Addisons
antibodies in Hashimotos
anti-TPO (thyroid peroxidase)
what cells mediate Hashimotos
T cells
cells seen in biopsy of Hashimotos
Askanazy cells
most common cause of hypothyroidism in developing world
Iodine deficiency
what is atrophic thyroiditis
diffuse lymphocytic infiltration of thyroid gland leading to
- hypothyroidism
- atrophy
- goitre
what is atrophic thyroiditis
diffuse lymphocytic infiltration of thyroid gland leading to
- hypothyroidism
- atrophy
- goitre
painful goitre + raised ESR
subacute thyroiditis
thyroid function tests in subclinical hypothyroidism
High TSH
Normal T3/T4
- patient on way to developing hypothyroidism but still has normal thyroxine levels
what is Sheehan syndrome
hypopituitarism following child birth due to hypovolaemic shock+ ischaemic necrosis
- massive post partum haemorrhage
- agalactorrhoea
- hypothyroidism
what is Riedel thyroiditis
fibrous tissue replacing normal thyroid parenchyma
- painless goitre
- hypothyroidism
treatment of hypothyroidism
Levothyroxine (T4 replacement)
starting dose of levothyroxine
25mcg OD and slowly titrated in patients >50 or those with cardiac disease
50-100mcg in all other patients
what happens to the dose of levothyroxine in pregnancy
increase by 25mcg
thyroid function tests in poor levothyroxine compliance
High TSH
Normal T3/T4
side effects of levothyroxine
hyperthyroidism in over treatment
reduced bone mineral density
Atrial fibrillation
Worsening of angina
what mood stabilising drug can cause hypothyroidism
lithium
what is myxoedema coma
medical emergency of hypothyroidism
- precipitated by illness/drugs
how does myxoedema coma present
confusion, hypothermia, bradycardia, hypotension, hypoglycaemia
symptoms of hyperthyroidism (thyrotoxicosis)
tachycardia/ palpitations heat intolerance dirarrhoea weight loss amenorrhoea tremor insomnia
symptoms of hyperthyroidism (thyrotoxicosis)
tachycardia heat intolerance dirarrhoea weight loss amenorrhoea tremor insomnia
thyroid function tests hyperthyroidism
Low TSH
High T3/T4
Most common cause of hyperthyroidism
Grave’s disease
antibodies in grave’s disease
Thyroid stimulating hormone receptor antibodies (TRAB)
Additional features of Grave’s disease
EYE DISEASE
- proptosis
- exophthalmos
- lid lag
Pre-tibial myoxedma
treatment of hyperthyroidism
carbimazole
beta blockers - symptomatic relief
radio iodine / surgery can also be used
important side effect of carbimazole
agranulocytosis
single hot nodule on isotope scan
toxic adenoma
what is a toxic adenoma
solitary thyroid nodule causing hyperthyroidism
- secretes T3
Treatment of toxic adenoma
radioiodine
globally reduced uptake on isotope scan
subacute thyroiditis (De Quervians)
- self limiting viral infection
- painful goitre
- fever
patchy uptake on isotope scan
toxic multi nodular goitre
what cardiac drug can cause hyperthyroidism
amiodarone
what drug can cause hyperthyroidism
amiodarone
thyroid function tests in sick euthyroid
Low TST
Low T3/T4
- Common in hospital patients
- Resolves upon recovery from systemic illness
what is a thyroid storm
life threatening emergency associated with hyperthyroidism
- precipitated by surgery, contrast CT, acute illness, trauma
symptoms of thyroid storm
temperature >38.5 seizures vomiting HTN confusion + agitation jaundice
treatment of thyroid storm
IV propanolol
IV dexamethasone
Antithyroid drugs e.g. methimazole
What is thyroid acropachy
triad of:
- finger clubbing
- soft tissue swelling of hands + feet
- periosteal new bone formation
what condition is thyroid acropachy seen in
Grave’s disease
Modifiable risk factor for reducing likelihood of developing thyroid eye disease
smoking
