4. Hyperthyroidism Flashcards
Graves disease
Autoimmune - antibodies bind to TSH receptors in lactotroph cells in AP
Smooth goitre + hyperthyroidism + exophthalmos + pretibial myxoedema
Presentation of Hyperthyroidism
- Weight loss + Low appetite
- Breathlessness
- Palpitations + tachy
- Sweating
- Heat intolerance
- Diarrhoea
- Lid lag + other sympathetic features
Nodular goitre (Plummer’s disease)
Caused by benign adenoma secreting thyroxine
No pretibial myxoedema/exophthalmos
Thyroid storm
50% mortality HYPERPYREXIA (>41 C) Accelerated tachy/arrhythmia Cardiac failure Delirium/psychosis Hepatocellular dysfunction -> jaundice
Treatment for hyperthyroidism
Anti-thyroid + Propranolol (non-selective beta blocker)
If unresponsive give RADIOIODINE
Example of anti-thyroid drug
Carbimazole (THIONAMIDE)
Inhibits thyroid peroxidase - stops iodination + coupling reactions -> REDUCED thyroxine synthesis
Also reduces peripheral conversion of T4 to T3
Clinical effect takes weeks because there’s already lots of thyroxine stored in colloid cells, plus long thyroxine half-life
Side effects: rashes, agranulocytosis (rare)
Aim to stop treatment after 18 months
Review patient’s thyroid function periodically
Which anti-thyroid drug is preferred in breastfeeding women?
Propylthiouracil
It is secreted less into breastmilk
Why do you co-administer propranolol with anti-thyroids?
To reduce the sympathetic effects of hyperthyroidism (tremors, tachy, anxiety)
Non-selective has better effet than beta1 blockers (atenolol)
Treatment for thyroid storm?
Potassium iodide
Given orally as Lugol’s solution (aqueous iodine)
Exploits the Wolff-Chaikoff effect: body shuts down thyroid hormone production in response to large dose of iodine
Inhibits thyroid peroxidase AND iodination of thyroglobulin
Hyperthyroid symptoms reduced within 1-2 days
Vascularity/size of gland reduced within 10 days
MAXIMUM EFFECTS after 10 days continuous admin.
DO NOT USE LONG-TERM (may turn on synthesis again)
Side effects: allergic reactions
Treatment for thyroid cancers?
Radioiodine (oral)
- Isotope I(131)
- Accumulates in colloid
- Emits radioactive beta particles
- DESTROYS FOLLICULAR CELLS
- Discontinue Anti-thyroid drugs 7-10 days prior to radioiodine treatment
- Radioactive half-life 8 days
- Radioactivity negligible after 2 months
Contraindication: NOT given to pregnant/breast-feeding women. Avoid contact with small children for several weeks.
Also given in very small doses (iv) for scanning the thyroid gland
What is Viral (de Quervain’s) Thyroiditis? Treatment?
Painful dysphagia, pyrexia, raised ESR (erythrocyte sedimentation rate)
Virus causes thyroid to stop making thyroxine and makes viruses instead
ZERO IODINE UPTAKE but stored thyroxine would still be released so toxicity still present
So radioiodine scan would show ZERO UPTAKE in thyroid
1 month later -> no more stored thyroxine -> HYPOTHYROIDISM
Back to normal after another month
Treatment: Steroids (anti-inflammatory) and possibly Propranolol to reduce symptoms
Patient has symptoms of hyperthyroidism, pyrexia, painful dysphagia, raised erythrocyte sedimentation rate.
Radioiodine scan shows no iodine uptake in thyroid.
A month later she comes back and has hypothyroidism.
Diagnosis? Treatment?
Viral thyroiditis
Give steroids, possibly propranolol to reduce symptoms
Patient is a mother of a 4 month old baby. She has nodular goitre, palpitations, tachy, sweating, diarrhoea, weight loss, low appetite. Diagnosis and treatment? What if that doesnt work?
Plummer’s disease -> hyperthyroidism
Give propylthiouracil (not carbimazole) with propranolol
If no improvement, radioiodine
Patient presents with hyperpyrexia, tachy, arrhythmia, jaundice. BP very high. Blood results confirm hyperthyroidism. Diagnosis and treatment?
Thyroid storm
Give Lugol’s solution (potassium iodide)
This should stimulate the Wolff-Chaikoff effect
