Hyperthyroidism & Graves Disease Flashcards
What is the definition of hyperthyroidism?
an over-production of thyroid hormone by the thyroid gland
hyperthyroidism is also sometimes called thyrotoxicosis
What is the definition of thyrotoxicosis?
an abnormal and excessive quantity of thyroid hormone in the body
What is the difference between primary and secondary hyperthyroidism?
primary:
* this is due to thyroid pathology
- the thyroid gland is producing excessive levels of thyroid hormone
secondary:
* the thyroid is producing excessive thyroid hormone as a result of overstimulation by TSH
- the pathology is within the hypothalamus or pituitary gland
What is Grave’s disease and how does it produce symptoms?
- an autoimmune condition in which TSH receptor antibodies cause a primary hyperthyroidism
- TSH receptor antibodies are produced by the immune system
- they mimic TSH and stimulate TSH receptors on the thyroid
this is the most common cause of hyperthyroidism
What is toxic multinodular goitre (Plummer’s disease) and how does it cause symptoms?
- multiple nodules develop on the thyroid gland
- the nodules all act independently of each other and the normal feedback system
- they continuously produce excessive thyroid hormone
What is meant by exopthalmos?
Why does it occur?
- the bulging of the eyeball out of the socket caused by Grave’s disease
- due to inflammation, swelling and hypertrophy of the tissue behind the eyeball
What is meant by pretibial myxoedema and why does it occur?
- there are deposits of mucin under the skin on the anterior aspect of the leg
- this produces a discoloured, waxy, oedematous appearance
- it is specific to Grave’s disease and is a reaction to TSH receptor antibodies
Who is typically affected by Grave’s disease?
women aged 30 - 50
What are the 4 main causes of hyperthyroidism?
- Grave’s disease
- toxic multinodular goitre
- solitary toxic thyroid nodule
- thyroiditis (e.g. Hashimoto’s / De Quervain’s)
What are the universal features of hyperthyroidism?
- sweating / heat intolerance
- tachycardia
- frequent loose stools
- sexual dysfunction
- fatigue
- weight loss
- anxiety / irritability
- oligomenorrhea
What features of hyperthyroidism are specific to Grave’s disease?
- diffuse goitre (without nodules)
- bilateral exophthalmos
- pretibial myxoedema
- thyroid acropachy
What is thyroid acropachy?
a triad of:
- digital clubbing
- soft tissue swelling of the hands and feet
- periosteal new bone formation
this occurs in < 1% patients with Grave’s disease
What features are unique to toxic multinodular goitre?
Who tends to be affected?
- most patients are aged > 50
- goitre with many firm nodules
this is the second most common cause of hyperthyroidism
What is a solitary toxic thyroid nodule?
- there is a single abnormal thyroid nodule that acts alone to release thyroid hormone
- usually a benign adenoma
- treated with surgical removal of the nodule
What are the features of De Quervain’s thyroiditis?
there is a presentation of a viral infection with:
- fever
- neck pain + tenderness
- dysphagia
- features of hyperthyroidism
What is the course of De Quervain’s thyroiditis typically like?
- initially there is a hyperthyroid phase
- TSH levels fall due to negative feedback
- this results in a subsequent hypothyroid phase
What is the treatment for De Quervain’s thyroiditis?
- the condition is self-limiting
- supportive treatment with NSAIDs for pain / inflammation
- beta-blockers may be given for symptomatic relief of hyperthyroidism
What is meant by “thyroid storm”?
- a rare and more severe presentation of hyperthyroidism
- it presents with pyrexia, tachycardia and delirium
this is life-threatening if not treated
How is thyroid storm managed?
- patient needs admission for monitoring
- it is treated in the same way as any other presentation of thyrotoxicosis
- supportive care with IV fluids, beta-blockers and antiarrhythmic medications may be required
Why does thyroid storm occur?
it occurs as a result of uncontrolled hyperthyroidism due to a major stress:
- infection
- trauma
- untreated / undertreated hyperthyroidism
- PE / CHF
- severe emotional distress
- DKA
- stroke
What is the first line treatment for hyperthryoidism (including Grave’s disease)?
carbimazole 40mg
- euthyroidism is typically achieved after 4-8 weeks
- the patient is then given a maintenance dose of carbimazole
When giving the maintenance dose of carbimazole, what 2 methods can be used for titration?
“titration-block”:
* the dose of carbimazole is titrated down from 40mg gradually to maintain euthyroidism
block-and-replace:
* a dose is given that is sufficient to block all thyroid hormone production
- the patient is given levothyroxine which is titrated to effect
How long must a patient take carbimazole for?
complete remission and the ability to stop taking carbimazole is usually achieved within 18 months
block and replace treatments tend to last for 6-9 months
What is the main side effect associated with carbimazole?
agranulocytosis
- a deficiency of granulocytes (i.e. neutrophils) in the blood
- this results in increased vulnerability to infection
What is the second-line treatment for hyperthyroidism?
propylthiouracil
- used in a similar way to carbimazole
- small risk of severe hepatic reactions, including death
carbimazole is preffered due to risk of severe hepatic reactions
How can radioactive iodine be used to treat hyperthyroidism?
- a single dose of radioactive iodine is drunk
- the radiation destroys a portion of cells within the thyroid
- the reduction in functioning cells results in decreased thyroid hormone production
this is usually used when patients relapse after ATD treatment or are resistant to it
What are the drawbacks of using radioactive iodine?
- remission can take up to 6 months
- patients can be left hypothyroid afterwards and require levothyroxine replacement
What are the rules that are in place when radioactive iodine treatment is used?
- must not be pregnant or get pregnant within 6 months
- must be > 16 years
- must avoid contact with children / pregnant women for 3 weeks after
- must avoid contact with anyone for several days after
When are beta-blockers used for the management of hyperthyroidism?
- used for symptomatic relief of adrenaline-related symptoms
- propanolol is preffered as it is non-selective
- treat the symptoms whilst the underlying treatment takes time to work
- particularly useful in thyroid storm
What is the only definitive treatment option for hyperthyroidism?
- surgery to remove the whole thyroid or any toxic nodules
- the patient will be left hypothyroid as thyroid hormone production is stopped
- they require life-long levothyroxine replacement
What drugs can cause hyperthyroidism?
amiodarone
What would you expect to see on TFTs in hyperthyroidism?
- low TSH
- high levels of T4 and T3
this is in primary hyperthyroidism
What are the 4 phases of De Quervain’s thyroiditis?
phase 1:
- hyperthyroidism, painful goitre, raised ESR
- lasts 3-6 weeks
phase 2:
* euthyroid for 1-3 weekw
phase 3:
* hypothyroid for weeks - months
phase 4:
* thyroid structure / function returns to normal
What investigation can be performed in De Quervain’s thyroiditis?
thyroid scintigraphy
- shows globally reduced uptake of iodine-131
What can rarely cause thyrotoxicosis in patients with pre-existing thyroid disease?
contrast
- patients with pre-existing thyrotoxicosis should not receive iodinated contrast
- this results in a large iodine load to the thyroid and hyperthyroidism developing over 2-12 weeks
What is meant by thyroid eye disease and why does it occur?
- there is an autoimmune response to an autoantigen (TSH receptor)
- this results in retro-orbital inflammation
- inflammation results in glycosaminoglycan and collagen deposition in the muscles
this affects 25-50% of patients with Grave’s disease
What risk factors increase the likelihood of thyroid eye disease?
- smoking is the most important modifiable RF
- radioiodine treatment may increase inflammatory symptoms (prednisolone reduces risk)
What are the features of thyroid eye disease?
- exophthalmos
- conjunctival oedema
- optic disc swelling
- ophthalmoplegia
- inability to close the eyelids results in sore, dry eyes
if this is untreated, there is a risk of exposure keratopathy
patients may be hypo-, eu- or hyperthyroid at time of presentation
What is exposure keratopathy?
damage to the cornea that occurs from prolonged exposure of the ocular surface to the outside environment
- can lead to ulceration, keratitis and permanent vision loss from scarring
What is involved in the management of thyroid eye disease?
- topical lubricants prevent corneal inflammation caused by exposure
- steroids (prednisolone)
- radiotherapy
- surgery
For patients with established thyroid eye disease, what red flag symptoms prompt urgent review by an opthalmologist?
- unexplained deterioration in vision
- obvious corneal opacity
- cornea still visible when eyes are closed
- disc swelling
- history of globe subluxation (eye suddenly popping out)
- awareness of change in intensity or quality of colour vision
