Hypothyroidism Flashcards
What is the definition of hypothyroidism? [2]
an underactive thyroid gland / where the thyroid gland does not produce enough thyroid hormone
What are the types of hypothyroidism? [4]
- primary hypothyroidism - due to disease of the thyroid gland
- secondary hypothyroidism - due to disease of the pituitary or hypothalamus
What are the 6 cause of hypothyroidism? [6]
- primary atrophic hypothyroidism - most common cause
- Hashimoto’s thyroiditis
- postpartum thyroiditis
- iatrogenic - thyroidectomy or radioiodine treatment
- drugs - amiodarone, carbimazole, lithium, iodine
- iodine deficiency - chief cause worldwide
What diseases/conditions is hypothyroidism associated with? [3, 3]
- autoimmune diseases - type 1 diabetes mellitus / Addison’s disease / pernicious anaemia
- Turner’s syndrome / Down’s syndrome / cystic fibrosis
What is the pathophysiology of primary atrophic hypothyroidism? [5]
associated with antithyroid autoantibodies / leading to lymphocytic infiltration of the thyroid / CD8+ T-cell mediated destruction / with atrophy and fibrosis / no goitre formation
What is the pathophysiology of Hashimoto’s thyroiditis? [4]
thyroid peroxidase antibodies (TPO-Ab) present in high titres / lymphocytic and plasma cell infiltration / atrophic changes with regeneration / goitre formation
How can amiodarone cause hypothyroidism? [2]
anti-arrhythmic drug can cause hypothyroidism as it inhibits the conversion of T4 to T3 / can also cause hyperthyroidism due to high iodine content
How can carbimazole cause hypothyroidism? [1]
antithyroid drug which blocks thyroid hormone synthesis
What is the pathophysiology of iodine deficiency? [3]
dietary iodine deficiency results in goitre formation / as borderline hypothyroidism leads to TSH stimulation / and thyroid enlargement
What are the symptoms of hypothyroidism? [10]
- tiredness
- lethargy
- cold intolerance
- weight gain
- low mood
- constipation
- menorrhagia
- dementia/decreased memory and cognition
- myalgia and weakness
- hoarse voice
What are the signs of hypothyroidism? [11]
- bradycardia
- reflexes relax slowly
- ataxia (cerebellar)
- dry, thin hair/skin
- yawning/drowsy/coma
- cold hands
- ascites
- round puffy face
- defeated demeanour
- immobile +/- ileus
- congestive cardiac failure
How can hypothyroidism be diagnosed? [3]
- thyroid function tests (TFTs)
- thyroid antibodies - thyroid peroxidase antibodies (TPO-Ab) in Hashimoto’s thyroiditis
- blood tests - macrocytic anaemia
What would you expect to find from TFTs results? [2]
high TSH / low T4 / (low T3)
What is the treatment for hypothyroidism? [3]
lifelong thyroid hormone replacement / oral levothyroxine (T4) / caution in elderly patients or those with ischaemic heart disease as may precipitate angina or MI
How is treatment monitored? [3]
- aim is to normalise but not suppress TSH
- primary hypothyroidism - dose titrated until TSH normalises / check T4 levels 6-8 weeks after dose adjustment
- secondary hypothyroidism - TSH will always be low / but T4 is monitored
