Thyrotoxicosis

Question 1

Define thyrotoxicosis

Answer 1

Syndrome resulting from excess circulating free T4 and/or T3

Question 2

What is the aetiology of thyrotoxicosis

Answer 2

Either due to increased thyroid hormone (hyperthyroidism) or increased release of stores thyroid hormone from and inflamed thyroid gland (thyroiditis)

Hyperthyroidism:
- Graves disease
- Toxic multinodular goitre
- Toxic adenoma
- TSH-secreting pituitary tumour (secondary hyperT)
- Drugs e.g. amiodarone, thyroxine
- Choriocarcinoma (raised hCG → binds to TSH receptors)

Thyroiditis:
- Post-partum
- de Quervain’s thyroiditis, presumed post-viral
- early-phase Hashimoto’s thyroiditis

Question 3

What are the risk factors for thyrotoxicosis

Answer 3

Hx autoimmune disease e.g. vitiligo, coeliac disease
FHx thyroid disease, diabetes, autoimmune disease

Question 4

What are the symptoms of thyrotoxicosis

Answer 4

Weight loss (Despite good appetite)
Fatigue, tiredness, lethargy
Anxiety and irritability
Palpitations
Sweating
Heat intolerance
Deteriorating school performance
Diarrhoea
Pruritus
Exertional dyspnoea
Menstrual irregularities
Decreased libido
Impotence in males
de Quervain’s thyroiditis - flu-like illness, tender goitre

Question 5

What are the signs of thyrotoxicosis on examination

Answer 5

Height and weight
Obs: irregular pulse, wide pulse pressure
General: restless, irritable, sweating, clubbing, pretibial myxoedema
ENT: goitre, bruit
Neuro: tremor, lid retraction, lid lag, proptosis, ophthalmoplegia, optic nerve atrophy, proximal muscle weakness, hyperreflexia

Question 6

What investigations should be done for thyrotoxicosis

Answer 6

Bloods:
- TFTs: TSH suppressed, T4/T3 raised
- TSH receptor antibodies: ?autoimmune thyrotoxicosis (Graves’)
- Thyroid peroxidase Abs (TPO): ?autoimmune thyrotoxicosis

Other
- US thyroid: Graves (diffusely enlarged), Nodule (focal enlargement)
- Technitium (Tc99m) or iodine uptake scan
- Bone age: may be advanced
- DEXA: reduced bone density

Question 7

What will be seen on technitium/iodine uptake scans for different causes of thyroiditis

Answer 7

Graves’: diffuse uptake
Toxic multinodular goitre/Plummer’s disease: multinodular gland with single hot nodule
Thyroid cancer: diffuse uptake with single cold nodule
De Quervain’s thyroiditis: no uptake

Question 8

What is the management for thyrotoxicosis

Answer 8

First line: antithyroid drugs e.g. carbimazole or propylthiouracil (PTU) - 1-4 years
- “block and replace” - ATDs to stop T4 production + thyroxine replacement
- “dose titration” - ATD dose adjusted so that hormone production is normalised
± propranolol (symptomatic)

Second line: radioiodine therapy (ablates the thyroid)

Third line: thyroidectomy (for large goitres causing upper airway obstruction or dysphagia or cannot take ATD) → permanent thyroid hormone replacement

Note: thyroiditis is usually self-limiting

Question 9

What is the management for thyrotoxic crisis/storm

Answer 9

1. Admit
2. IV fluids
3. ATD e.g. pTU ± iodine (potassium iodide/Lugol’s iodine)
4. Propranolol
5. Hydrocortisone (risk of adrenal insufficiency)
6. treat any precipitating factors e.g. infection

Question 10

What are the complications of thyrotoxicosis

Answer 10

Thyroid storm: acute and life-threatening thyrotoxicosis, often caused by precipitating event
- Fever, tachycardia, confusion, agitation, nausea, HTN
ATD use → agranulocytosis