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Lecture Notes - Endocrinology > Thyrotoxicosis > Flashcards

Thyrotoxicosis Flashcards

1
Q

What is thyrotoxicosis

A

The syndrome resulting from an excess of circulating free thyroxine (T4) and / or free triiodothyronine (T3)

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2
Q

What might cause thyrotoxicosis

A

Either increased thyroid hormone synthesis (hyperthyroidism) or
Increased release of stored thyroid hormone from an inflamed thyroid gland (subacute thyroiditis

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3
Q

What is primary hyperthyroidism characterised by

A

Raised free T4 and or T3 and low TSH

TSH is suppressed due to the negative feedback effect of thyroid hormones on TSH synthesis / secretion

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4
Q

What is secondary hyperthyroidism characterised by

A

Raised T4 and T3 due to increased TSH secretion from a pituitary tumour

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5
Q

Wyat is subclinical hyperthyroidism defined as

A

Suppressed TSH in the presence of normal free T4 and T3

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6
Q

What accounts for the majority of hyperthyroidism

A

Grave’s disease

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7
Q

What is the most common cause of hyperthyroidism in the elderly

A

Toxic multinodular goitre

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8
Q

What are some of the causes of thyrotoxicosis

A 
Grave's disease 
Toxic multinodular goitre 
Toxic adenoma 
Thyroiditis 
Secondary hyperthyroidism 
Metastatic thyroid cancer
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9
Q

What causes Grave’s disease

A

Autoantibodies that stimulate the TSH receptor and hence thyroid hormone synthesis and secretion, and thyroid growth

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10
Q

What are some precipitating and predisposing factors of Grave’s disease

A 
Genetic susceptibility (association with certain alleles of CTLA-4 and HLA)
environmental factors such as infection
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11
Q

What are toxic multi nodular goitre and toxic adenoma the result of

A

Focal and / or diffuse hyperplasia of thyroid follicular cells whose function is independent of regulation by TSH

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12
Q

How can thyroiditis resit in thyrotoxicosis

A

By the release of preformed thyroid hormones from a damaged thyroid gland into the circulation

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13
Q

How can amiodarone affect thyroid function

A

Inhibits the conversion of T4 to T3

Results in a high or high-normal free T4

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14
Q

What are the clinical presentations of a patient with thyrotoxicosis

A

Heat intolerance, anxiety, irritability, hyperactivity, fatigue, insomnia
Increased sweating, warm moist skin, palmar erythema
Onycholysis, hair loss
Eyelid retraction or lag, proptosis, periorbital oedeama, increased tear production
Plaplitations
Widened pulse pressure
Exertional breathlessness
Diarrhoea, increased appetite, weight loss, dysphagia
Tremor, proximal muscle weakness, brisk tendon reflexes, inability to concentrate
Depression
Oligomennorhoea
Gynaecomastia, reduced libido, erectile dysfunction, polyuria
Osteoporosis
Goitre!

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15
Q

What is the pathogenesis of Graves’ ophthalmopathy

A

Involves activated T cell cytokines and TSH receptor antibodies that activate TSH receptors on fibroblasts and adipocytes. This sets of an inflammatory process and causes the secretion of hydrophilic glycosaminoglycans, resulting in an increased retro-orbital volume

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16
Q

What is a condition that is specific to Graves?

A

Pretirbial myxoedema

Results from an accumulation of hydrophilic glucosaminoglycans secreted by fibroblasts in the dermis

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17
Q

Describe the appearance of pretibila myxoedema

A

Raised, pigmented, orange-peel textured joules or plaques on the anterior aspect of the leg or the dorsum of the foot
Usually asymptomatic but may be pruritic or painful

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18
Q

What does thyroid acropachy resemble

A

Clubbing

Due to periosteal new bone formation in the phalanges

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19
Q

What is a thyroid storm also known as

A

Thyrotoxic crisis

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20
Q

How might a thyroid storm present

A

Fever, sweating
Cardiovascular symptoms: tachyarrhythmias, cardiac failure
Neuro: agitation, delirium, seizure, coma
GI : diarrhoea, vomiting, jaundice

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21
Q

What might cause a thyroid storm

A

Thyroid surgery, radio-iodine, iodinated contrast agents, withdraw of thionamides (antithyroid drugs) and acute illnesses including infection, stroke DKA or trauma

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22
Q

What are some investigations for thyroxicosis

A

Thyroid function tests:

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23
Q

What thyroid function test results diagnose primary hyperthyroidism

A

Suppressed serum TSH and high free T4 and or free T3

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24
Q

What thyroid function test results indicate secondary hyperthyroidism

A

TSH is either high or inappropriately normal in the presence of raised T4/T3

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25
Q

What thyroid function test results indicate subclinical hyperthyroidism

A

TSH is low, but free T4 and T3 levels are normal

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26
Q

What investigation is useful in differentiating between different causes of thyrotoxicosis

A

Radioisotope uptake scan

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27
Q

What is characterised by a diffuse increased uptake of the radioisotope

A

Grave’s disease

28
Q

What would be seen if a toxic multi nodular goitre was present on radioisotope uptake scan

A

Multiple areas of increased radioisotope uptake with suppression of uptake in the rest of the gland

29
Q

What would be seen if a solitary adenoma was present on radioisotope uptake scan

A

Single area of increased radioisotope uptake with suppression of uptake i the rest of the gland

30
Q

What would be seen if thyroiditis was present on radioisotope uptake scan

A

A low or absent radioisotope

31
Q

What must patients not take prior to a radioisotope uptake scan

A

Any iodine-containing medications, supplements or radio contrast dyes
MUST not be pregnant

32
Q

What form of antibodies are positive in Grave’s disease

A

TSH receptor-stimulating antibodies

Test is expensive

33
Q

What is elevated in patients with subacute viral de Quervain’s thyroiditis

A

Erythrocyte sedimentation rate (ESR)

34
Q

What should be requested in cases of secondary hyperthyroidism

A

A pituitary MRI

35
Q

What are the 3 options for treatment in thyrotoxicosis

A

Antithyroid drugs (thionamides)
Radio-iodine
Surgery (thyroidectomy)

36
Q

What else could be give for patients with severe thyrotoxic symptoms

A

Beta blockers e.g. propranolol

37
Q

What is the treatment for Grave’s disease in those below 50

A

Antithyroid drugs as initial treatment

if thyrotoxicosis relapses, surgery or radio-iodine is preferred

38
Q

What is the treatment for Graves’ disease in those over 50

A

Radio-iodine or surgery

39
Q

What is the primary treatment for men with Graves’ disease

A

Radio-iodine due to the high relapse rate in men

40
Q

How are patients with toxic multi nodular goitre and toxic adenoma treated

A

Ideally with radio-iodine or surgery depending on patient’s preference
Anti-thyroid drugs may be used in those who refuse or are unsuitable for surgery

41
Q

What are some antithyroid drugs

A

carbimazole
methimazole
propylthiouracil (PUT)

42
Q

How do antithyroid drugs work

A

They reduce T4 and T3 production by inhibiting thyroid peroxidase

43
Q

What is an advantage of taking carbimazole over other drugs

A

Only has to be taken once daily

44
Q

Describe the dosage of antithyroid drugs in Graves’ disease

A

Titration regimen

Start of high and gradually reduce over 4-8 weeks to maintenance dose

45
Q

What is a rare but significant complication of antithyroid drugs

A

Agranulocytosis

46
Q

What are the symptoms of agranulocytosis

A

Fever
sore throat
mouth ulcers
any sign of infection

47
Q

What is some advice for patients with suspected agranulocytosis

A

Stop treatment immediately

Full blood count checked ASAP

48
Q

What might happen if a patient with agranulocytosis has a neutrophil count of less than 0.5x10^9/L and a sore throat

A

May required admission and treatment with granulocyte colony-stimulating factor and antibiotics

49
Q

What are a common side effect of antithyroid drugs. What should be done for this

A

Rashes and pruritus

Treat with antihistamines without stopping treatment

50
Q

What are some other side effects of antithyroid drugs

A 
Macular rash 
Nausea 
vomiting 
abnormal taste/ smell 
arthralgia 
pruritus 
lymphadenopathy 
deranged LFTs
51
Q

PTU may rarely be associated with what

A

Anti-neutrophil cytoplasmic antibody positive vasculitis

52
Q

How often should a patient on an antithyroid drug regimen be followed up

A

6 weekly for 6 months
6 monthly for 2 years
Annually

53
Q

How is radio-iodine administered

A

Orally as a capsule or solution

54
Q

How long do antithyroid drugs need to be discontinued for prior to radio-iodine commencing

A

about 3 days

This allows uptake of the isotope by the thyroid gland

55
Q

What happens to the dose in patients with renal failure

A

It must be significantly reduced

56
Q

Why is radio=iodine contraindicated in pregnancy and breast feeding

A

It destroys fetal thyroid

57
Q

How long must a patient who has received radio-iodine treatment wait before conceiving

A

4 months

58
Q

Radio-iodine is associated with an exacerbation of what

A

Graves’ ophthalmopathy

59
Q

Why is surgery not an ideal treatment for Graves’

A

It is associated with a higher rate of hypothyroidism or recurrent hyperthyroidism depending on how much of the thyroid is removed

60
Q

What are some of the risks associated with thyroid surgery

A

Hypoparathyroidism
recurrent laryngeal nerve damage
laryngeal oedema (due to bleeding int the neck )

61
Q

In what cases is surgery chosen over radio-iodine

A

Patients with large goitres causing upper airway obstruction or dysphagia
Patients who cannot take antithyroid drugs and are either pregnant or have moderate/ severe Graves’ ophthalmopathy

62
Q

What is the treatment for mild ophthalmopathy symptoms

A

Artificial tears during the day and ointments
eye shades
elevation of the head and neck
avoid sleeping on the face

63
Q

What is the treatment for severe ophthalmopathy symptoms

A

IV methylprednisolone
decompression surgery
radiotherapy

64
Q

How is subacute and postpartum thyroiditis treated

A

NSAIDs if mild

Steroids and NSAIDs for moderate or severe

65
Q

How is thyroid hormone resistance characterised by

A

Reduced responsiveness of the tissues to thyroid hormone

66
Q

What symptoms of thyroid hormone resistance may patients present with

A 
Goitre 
Tachycardia 
ADHD , learning disability 
Growth retardation 
Recurrent ENT infection

Lecture Notes - Endocrinology (40 decks)

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