Hyperthyroidism Flashcards
Define hyperthyroidism
Caused by an overactive thyroid gland causing an excess of thyroid hormone (T3 and T4)
Hyperthyroidism is most commonly affects which gender?
Women
Define thyrotoxicosis
Refers to an excess of thyroid hormone, having an overactive thyroid gland is not a prerequisite (e.g. consumption of thyroid hormone)
Name three primary causes of hyperthyroidism
Primary meaning it is caused by thyroid dysfunction
- Graves’ disease
- Toxic multinodular goitre
- Radiation
Name two secondary causes of hyperthyroidism
Secondary meaning it is not caused by thyroid dysfunction
- Drugs e.g. Lithium
- Gestational hyperthyroidism
What is the most common cause of hyperthyroidism
Graves’ disease
Describe the pathogenesis of Graves Disease
Caused by IgG antibodies to the TSH receptors found within the thyroid – known as TSHR-Ab
TSHR-Ab mimic the action of TSH causing excessive stimulation of the gland
What is the second most common cause of hyperthyroidism
Toxic multinodular goitre
Describe the pathogenesis of toxic multinodular goitre
Characterised by multiple nodules that develop on the thyroid gland develop that are capable of secreting thyroid hormone
Acts independently of feedback system and therefore results in the continuous production of excessive thyroid hormone
Name some of the symptoms of hyperthyroidism
Goitre
Palpitations
Heat intolerance
Weight loss
Diarrhoea
Amenorrhoea
Reduced libido
Gynaecomastia (in men)
Fatigue
Name some of the signs of hyperthyroidism
- Goitre
- Sinus tachycardia/arrhythmias
- Hair loss
- Palmar erythema
- Tremor
- Thyroid bruit (Graves’)
- Myxoedema - deposition of mucopolysaccharides in the skin leading to swelling.
What is the other name given to thyroid storm
Thyrotoxic crisis
Define thyroid storm
Hypermetabolic state induced by excessive release of thyroid hormones
What are the triad of symptoms for thyroid storm
High blood pressure
High temperature
Tachycardia
How is the thyroid storm managed
Symptom control with IV propranolol
Reduced thyroid activity with PPU
Why is PPU the preferred treatment for thyroid storm
Preferred as it inhibits peripheral thyroxine conversion
What are the three unique features associated with Graves Disease
Diffuse goitre (without nodules)
Graves’ ophthalmopathy
Pretibial myxoedema
Features caused by the presence of TSH receptor antibodies
Describe the pathogenesis of pretibial myxoedema
Infiltrative dermopathy resulting from deposition of mucin in the dermis on the anterior aspects of the leg (pre-tibial area)
What are the biochemistry results for primary hyperthyroidism
Low TSH
High fT4 + fT3
What are the biochemistry results for subclinical hyperthyroidism
Low TSH
Normal T3/4
What are the biochemistry results for pituitary adenoma
High TSH
High T3/4
What is the autoantibodies associated with Graves Disease
Thyroid stimulating hormone receptor antibodies (TSHR-Ab)
What are the two imaging techniques used to investigate the thyroid
Ultrasonography
Thyroid uptake scan
Name the three components of hyperthyroidism management
- Medical therapy
- Anti-thyroid drugs (thioamides)
- Symptom relief
- Radio-iodine
- Surgery
What is the first line anti-thyroid drugs (thioamides)
Carbimazole
What are the names of the two types of anti-thyroid drugs
Carbimazole
Propylthiouracil (PPU)
What is the second line anti-thyroid drug used in managing hyperthyroidism
Propylthiouracil (PPU)
When is Propylthiouracil (PPU) the first line anti-thyroid drug?
Patient is intolerant to carbimazole
In first trimester of pregnancy
In thyroid storm
What is a potential side effect of Propylthiouracil (PPU)
Small risk of severe hepatic reactions
Name the two anti-thyroid drug regiments
Titration
Block and replace
Describe the titration anti-thyroid drug regiment
Dose is carefully titrated to maintain normal levels of T3/T4
Describe the block and replace anti-thyroid drug regiment
Carbimazole is given at a level sufficient to block endogenous T3/T4 production and the patient takes levothyroxine titrated to effect
What drug is used in symptom relief in hyperthyroidism
Propranolol (non-selective beta blocker)
Blocks the adrenalin related symptoms of hyperthyroidism
Why does the beta blocker used in the symptom relief of hyperthyroidism have to be non-selective
Non-selective beta blockers because they block adrenergic activity as opposed to more “selective” beta blockers that work only on the heart
Radio-iodine is offered first line in what patient groups?
[Hyperthyroidism]
Graves’ disease in those suitable and not likely to enter remission
Toxic multinodular goitre
How does radio-iodine work as a treatment for hyperthyroidism
Involves drinking a single dose of radioactive iodine – the iodine is taken up by the thyroid gland and the emitted radiation destroys a proportion of the thyroid cells reducing the thyroid hormone production
Name a side effect of radio-iodine
Hypothyroidism requiring levothyroxine replacement
When is radio-iodine contraindicated
Contraindicated in Graves eye disease because it may worsen symptoms
Name three potential complications of thyroidectomy
Hypocalcaemia - due to the proximity of parathyroid gland to the thyroid gland.
Recurrent laryngeal nerve injury
Hypothyroidism
Name some complications of hyperthyroidism
Thyroid storm (often precipitated by surgery, trauma or infection)
Atrial fibrillation
High output heart failure
Osteopenia/osteoporosis
Upper airway obstruction due to a large goitre
Corneal ulcers/visual loss in Graves’ eye disease
Thyrotoxicosis without hyperthyroidism does not feature overactivity of the thyroid gland.
Name two conditions can cause thyrotoxicosis without hyperthyroidism
Thyroiditis: inflammation of the thyroid gland resulting in the release of stored thyroid hormone.
Exogenous ingestion: a person ingests thyroid hormone.
What is De Quervain’s (subacute granulomatous) thyroiditis
Hyperthyroidism following a viral infection
Results in inflammation of the thyroid gland and release of thyroid hormone
Self-limiting - resolves on its own
Name the characteristic feature of De Quervain’s thyroiditis
characteristically causes a painful goitre
