Hypothyroidism Flashcards
What is another word for hypothyroidism?
myxoedema
What gender is it more common in?
females (5-10 times)
What are the causes of hypothyroidism?
- Iodine deficiency (chief worldwide cause)
2. Autoimmune - atrophic, Hashimoto’s thyroiditis
What is autoimmune HT associated w?
other autoimmune diseases e.g. DMT1, Addison’s, pernicious anaemia
What conditions is hypothyroidism associated w in general?
Turner’s
Downs
CF
PBC
Explain the pathophysiology behind primary atrophic HT
Anti-thyroid autoabs lead to lymphoid infiltration of the gland and eventual atrophy and fibrosis
How would u differentiate between primary atrophic HT and Hashimotos thyroiditis?
Atrophic - NO GOITRE
Hashimotos - GOITRE (lymphocytic + plasma cell infiltration)
Explain the pathophysiology behind hashimotos
thyroid peridoxase abs present in HIGH titres (enzyme needed for production + storage of thyroid hormone)
What age Is usually affected in hashimotos?
60-70
What is postpartum thyroiditis?what can it be mistaken as? what test would u do to differentiate?
- transient phenomenon after pregnancy
can cause hyper or hypothyroidism (or both sequentially)
Normally self-limiting, when abs are found - high chance of permanent - Postpartum depression
- Do TFTs
What are iatrogenic causes of HT?
Thyroidectomy - rx of hyperthyroidism or goitre
Radioactive iodine rx or external neck irradiation for head + neck cancer
What drugs can cause HT?
- Carbimazole
- Lithium
- Amiodarone
What are the sx ?
- Hoarse voice
- Goitre
- Constipation
- Cold intolerant
- Weight gain
- Menorrhagia
- Myalgia, weakness
- Tired, low mood, dementia
- Myxoedema
What is myxoedema?
deposition of mucopolysaccharides in the dermis resulting in swelling of the affected area
What are the signs?
BRADYCARDIC: Bradycardia Reflexes relax slowly Ataxia Dry, thin hair/skin Yawning/drowsy/coma Cold hands +/- temp drop Ascites Round puffy face Defeated demeanour Immobile +/- ileus CCF
How may children present ?
slow growth
poor school performance
arrest in puberty
How can young women present?
may have oligomenorrhoea amenorrhoea menorrhagia infertility hyperprolactinaemia
How would u test? What is diagnostic of hypothyroid state
- TFTs - high TSH, serum free T4 low - DIAGNOSTIC
- Thyroid abs + organ specific abs e.g. TPO-Ab in Hashimotos
- FBC - normochromic
normocytic - Hypercholesterolaemia
What is the treatment?
ORAL LEVOTHYROXINE (T4)
How is treatment monitored?
titrate until TSH normalises
Check T4 levels 6-8 weeks after dose adjustment
When should a lower dose of treatment be given?
in those w CAD - can exacerbate angina or MI
elderly
What medication is known to cause hypothyroidism? what is the management?
amiodarone - iodine-rich, can inhibit T4 release
rx: stop amiodarone, glucocorticoids, thyroidectomy if drug can’t be discontinued
What is the main hypothyroid emergency?
myxoedema coma
what can precipitate myxoedema coma?
infection
MI
stroke
trauma
What are the signs + sx of myxoedema coma?
Looks hypothyroid Hypothermia Hypoglycaemia Bradycardia Coma (psychosis may precede) Seizures usually >65yrs
What can u find on examination in myxoedema coma?
Goitre
Cyanosis
HF
Signs of precipitants
What is Rx of myxoedema coma?
IV T3 (liothyronine) slowly 5-20mcg/12hrs
Correct hypoglycaemia
IV hydrocortisone if pituitary cause suspected
Active warming
When would u suspect a thyroid cause of myxoedema coma?
goitre
previous radio iodine
prev thyroid surgery
What is involved in further r xox myxoedema coma?
T3 until sustained improvement then levothyroxine
Hydrocortisone + IV fluids as needed
T3 + T4 which is converted to which and which is the active form used by cells?
T4 -> T3, T4 is secreted in larger amounts than T3 but T3 is active form
