Endo - Thyroid Disorders Flashcards
What level of TSH is found in a patient with hypothyroidism + the thyroid gland has been destroyed by immune system?
high TSH
What is Graves’ disease?
→ autoimmune
→ antibodies bind to + stimulate TSH receptor
→ cause goitre (smooth) + hyperthyroidism
What are signs of Graves’ disease?
→ being warm + sweaty (heat intolerance) → tachycardia → exophthalmus → smooth enlarged goitre → increased bowel activity → weight loss despite increased appetite → oligomenorrhea / amenorrhea → pretibial myxedema → lid lag + other sympathetic features → breathlessness
What causes exophthalmus?
antibodies bind to muscles behind the eye causing bulge
What’s pretibial myxoedema?
other antibodies causes hypertrophy + swelling + growth of soft tissue at shins
What is myxedema?
severely advanced hypothyroidism
What does the thyroid gland look like in Graves’ Disease?
→ diffused enlargement + engorgement of smooth goitre
→ diffused goitre of large size after radioiodine uptake + sometimes in pyramidal lobe
What are the symptoms of Plummer’s Disease?
→ Toxic nodular goitre → NOT autoimmune → Benign adenoma that is overactive at making thyroxine. → NO pretibial myxoedema → NO exophthalmos
What does the thyroid gland look like in Plummer’s Disease?
→ only nodule is swollen due to hyperplasia
→ one-sided swelling on goitre, not very smooth, even after radioiodide uptake
What are the effects of thyroxine on the SNS?
→ sensitises beta adrenoreceptors to ambient levels of adrenaline + noradrenaline
→ causes apparent sympathetic activation
→ tachycardia, palpitations, tremor in hands, lid lag
What is a thyroid storm?
→ untreated hyperthyroidism
→ medical emergency
→ 50% mortality rate
What are the symptoms of a thyroid storm?
→ Hyperpyrexia > 41oC → accelerated tachycardia / arrhythmia → cardiac failure → delirium / frank psychosis → hepatocellular dysfunction; jaundice
What are the drugs used to treat hyperthyroidism?
→ the thionamides (thiourylenes; anti-thyroid drugs) - propylthiouracil (PTU) - carbimazole (CBZ) → Potassium Iodide → Radioiodine → β-blockers (for symptoms)
What are the drugs used to treat hyperthyroidism?
→ the thionamides (thiourylenes; anti-thyroid drugs) - propylthiouracil (PTU) - carbimazole (CBZ) → Potassium Iodide → Radioiodine → β-blockers (for symptoms)
How do thioamides treat hyperthyroidism?
→ inhibition of TPO (thyroid perioxidases)
→ stops T3 + T4 synthesis
→ biochemical effect = hours
→ clinical effect = weeks
What are the unwanted side effects of thioamides?
→ agranulocytosis (usually reduction in neutrophils) - rare and reversible on withdrawal of drug.
→ rashes (relatively common)
How do you follow up on a patient taking thioamides?
→ Usually aim to stop anti-thyroid drug treatment after 18 months
→ Review patient periodically including DTFT (dynamic thyroid function tests) for remission/relapse
When is iodide used to treat hyperthyroidism?
→ preparation of hyperthyroid patients for surgery
→ severe thyrotoxic crisis (thyroid storm)
How is iodide used to treat hyperthyroidism?
→ inhibits iodination of thyroglobulin
→ inhibits H2O generation + thyroperioxidase
→ inhibition of thyroid hormone synthesis + secretion
→ WOLF-CHAIKOFF effect - presumed auto-regulatory effect
→ symptoms reduce within 1-2 days
→ gland reduces in vascularity + size 10-14 days
What are the risks of a thyroidectomy?
→ Risk of voice change
→ Risk of also losing parathyroid glands
→ Scar
→ Anaesthetic
What are the names of the two thionamides?
- propylthiouracil (PTU)
- carbimazole (CBZ)
How much radioiodine is given to someone?
capsule of approx. 370 MBq (10mCi) of isotope I (131)
What are the directions of use of radioiodine?
→ contraindicated in pregnancy
→ need to avoid children + pregnant women for 10 days
What is an option of radioiodine only for scans, not treatment?
99-Tc pertechnetate
What is Viral (de Quervain’s) thyroiditis?
viral infection of the thyroid
What are the symptoms of viral thyroiditis?
→ Painful dysphagia
→ Hyperthyroidism
→ Pyrexia (fever)
→ Thyroid inflammation (enlarged more on one side)
How does viral thyroiditis cause hyperthyroiditis?
→ Virus attacks thyroid gland causing pain and tenderness
→ all stored thyroxine is released - hyperthyroidism
→ Thyroid stops making thyroxine and makes viruses instead
→ Thus ZERO iodine uptake
Why is iodine given to a patient before a thyroidectomy?
→ gland is overactive, highly vascularised - would bleed a lot if cut into
→ iodine makes the gland normal for ten days (paler, firmer, less likely to bleed and tear as much)\
→ however, only for ten days
Why does a viral thyroiditis patient become hypothyroidic after 4 weeks?
→ virus makes the thyroid make thyroid gland make more virus instead of thyroxine
→ all stores of thyroxine deplete in a month so patient becomes hypothyroidic
What does the thyroid gland look like in viral thyroiditis radiologically after iodine uptake?
→ there is no iodine uptake
→ so comes up BLANK
How is viral thyroiditis treated?
→ after three months of the hypothyroid phase, there should be slow recovery of patient and their thyroid gland
→ giving anti-thyroid or thyroid medication could have unnecessary outcomes
