Hypothyroidism Flashcards
what can be measured to investigate thyroid pathology
TSH(reflects tissue thyroid hormone action), free T3 and free T4
what thyroid hormone and TSH levels are seen in primary hypothyroidism
free T3 and T4 are low, TSH is high
what thyroid hormone and TSH levels are seen in secondary hypothyroidism
free T3 and T4 are low, TSH is low/normal
what is hypothyroidism
any disorder that results in insufficient secretion of thyroid hormones from thyroid gland
what is myxoedema
refers to severe hypothyroidism, a medical emergency
in what groups of people is incidence of hypothyroidism higher
women 5-10 times more than men, >60 increased risk, white > hispanic/african-american, higher in areas of high iodine intake
what are the different types of causes for primary hypothyroidism
goitrous, non-goitrous or self-limiting
give examples of goitrous causes of primary hypothyroidism
chronic thyroiditis(Hashimoto’s), iodine deficiency, drug induced(eg amiodarone)
give examples of non-goitrous causes of primary hypothyroidism
atrophic thyroiditis, post-ablative therapy
give examples of self-limiting causes of primary hypothyroidism
withdrawal of antithyroid drugs, post-partum thyroiditis
what is usually the cause of secondary hypothyroidism
diseases of the hypothalamus or pituitary gland
many of these!
what is the most common cause of hypothyroidism in the western world
Hashimoto’s thyroiditis(autoimmune thyroiditis)
describe what Hashimoto’s thyroiditis is
autoimmune destruction of the thyroid gland and reduced thyroid hormone production
what is Hashimoto’s thyroiditis characterised by
antibodies against thyroid perxidase(TPO) and T cell infiltrate and inflammation under microscope
what gender is Hashimoto’ s thyroiditis seen in more commonly, and what is often in their FH
female > male, often FH of autoimmune thyroiditis or other autoimmune disease
what hair and skin clinical features are associated with hypothyroidism
coarse/sparse hair, periorbital puffiness, pale cool skin/feels doughy to touch, vitiligo may be present, dull/expressionless face
what thermogenesis and fluid retention clinical features are associated with hypothyroidism
cold intolerance and pitting oedema
what cardiac clinical features are associated with hypothyroidism
reduced HR, cardiac dilatation, pericardial effusion, worsening of HF
what metabolic clinical features are associated with hypothyroidism
hyperlipidaemia, decreased appetite, weight gain
what GI clinical features are associated with hypothyroidism
constipation, megacolon, intestinal obstruction
what respiratory clinical features are associated with hypothyroidism
deep hoarse voice, macroglossia, obstructive sleep apnoea
what are some of the neurological/CNS clinical features are associated with hypothyroidism
decreased intellectual/motor activities, depression, muscle stiffness, cramps, peripheral neuropathy, carpal tunnel syndrome
what gynae/reproductive clinical features are associated with hypothyroidism
menorrhagia, later oligo- or amenorrhea, hyperprolactinaemia
what thyroid autoantibodies are used in autoimmune hypothyroidism diagnosis, and how often are they seen
anti-TPO antibody(95%), anti-thyroglobulin antibody(60%), TSH receptor antibody(10-20%)
how quickly should normal metabolic rate be achieved in a hypothyroidism patient and why
restores gradually, as rapid restoration can precipitate cardiac arrhythmias
what pharmacological therapy should be used for young patients with hypothyroidism
levothyroxine 50-100ug daily, adjusted every 4 weeks according to response
what pharmacological therapy should be used for elderly patients with history of IHD
levothyroxine 25-50ug daily, adjusted every 4 weeks according to response
how often should TSH of patients on treatment be tested
2 months after any dose change, but if patient is stabilised every 12-18 months
what is the main treatment for hypothyroidism and when should it be taken
levothyroxine(T4), should be taken before breakfast
how may dose requirement for levothyroxine change in pregnancy
can increase by 25-50%
how is dose of levothyroxine on secondary hypothyroidism different to that of primary
TSH unreliable in secondary, titrate dose of levothyroxine to free T4 level
in what patients is myxoedema coma typically seen in
elderly women with long standing unrecognised or untreated hypothyroidism
(mortality is 60%)
what findings are seen in myxoedema coma
ECG = bradycardia, heart block, T inversion, QT prolongation
Type 2 resp failure = hypoxia. hypercarbia
10% have adrenal failure
what treatment is used for myxoedema coma patients
intensive care, passively warm them, cardiac/fluid/U&E/BP/BG monitoring, broad antibiotics, thyroxine cautiously(hydrocortisone)
