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Lecture Notes - Endocrinology > Thyrotoxicosis > Flashcards

Thyrotoxicosis Flashcards

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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
What thyroid function test results indicate subclinical hyperthyroidism
TSH is low, but free T4 and T3 levels are normal
26
What investigation is useful in differentiating between different causes of thyrotoxicosis
Radioisotope uptake scan
27
What is characterised by a diffuse increased uptake of the radioisotope
Grave's disease
28
What would be seen if a toxic multi nodular goitre was present on radioisotope uptake scan
Multiple areas of increased radioisotope uptake with suppression of uptake in the rest of the gland
29
What would be seen if a solitary adenoma was present on radioisotope uptake scan
Single area of increased radioisotope uptake with suppression of uptake i the rest of the gland
30
What would be seen if thyroiditis was present on radioisotope uptake scan
A low or absent radioisotope
31
What must patients not take prior to a radioisotope uptake scan
Any iodine-containing medications, supplements or radio contrast dyes MUST not be pregnant
32
What form of antibodies are positive in Grave's disease
TSH receptor-stimulating antibodies | Test is expensive
33
What is elevated in patients with subacute viral de Quervain's thyroiditis
Erythrocyte sedimentation rate (ESR)
34
What should be requested in cases of secondary hyperthyroidism
A pituitary MRI
35
What are the 3 options for treatment in thyrotoxicosis
Antithyroid drugs (thionamides) Radio-iodine Surgery (thyroidectomy)
36
What else could be give for patients with severe thyrotoxic symptoms
Beta blockers e.g. propranolol
37
What is the treatment for Grave's disease in those below 50
Antithyroid drugs as initial treatment | if thyrotoxicosis relapses, surgery or radio-iodine is preferred
38
What is the treatment for Graves' disease in those over 50
Radio-iodine or surgery
39
What is the primary treatment for men with Graves' disease
Radio-iodine due to the high relapse rate in men
40
How are patients with toxic multi nodular goitre and toxic adenoma treated
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
What are some antithyroid drugs
carbimazole methimazole propylthiouracil (PUT)
42
How do antithyroid drugs work
They reduce T4 and T3 production by inhibiting thyroid peroxidase
43
What is an advantage of taking carbimazole over other drugs
Only has to be taken once daily
44
Describe the dosage of antithyroid drugs in Graves' disease
Titration regimen | Start of high and gradually reduce over 4-8 weeks to maintenance dose
45
What is a rare but significant complication of antithyroid drugs
Agranulocytosis
46
What are the symptoms of agranulocytosis
Fever sore throat mouth ulcers any sign of infection
47
What is some advice for patients with suspected agranulocytosis
Stop treatment immediately | Full blood count checked ASAP
48
What might happen if a patient with agranulocytosis has a neutrophil count of less than 0.5x10^9/L and a sore throat
May required admission and treatment with granulocyte colony-stimulating factor and antibiotics
49
What are a common side effect of antithyroid drugs. What should be done for this
Rashes and pruritus | Treat with antihistamines without stopping treatment
50
What are some other side effects of antithyroid drugs
``` Macular rash Nausea vomiting abnormal taste/ smell arthralgia pruritus lymphadenopathy deranged LFTs ```
51
PTU may rarely be associated with what
Anti-neutrophil cytoplasmic antibody positive vasculitis
52
How often should a patient on an antithyroid drug regimen be followed up
6 weekly for 6 months 6 monthly for 2 years Annually
53
How is radio-iodine administered
Orally as a capsule or solution
54
How long do antithyroid drugs need to be discontinued for prior to radio-iodine commencing
about 3 days | This allows uptake of the isotope by the thyroid gland
55
What happens to the dose in patients with renal failure
It must be significantly reduced
56
Why is radio=iodine contraindicated in pregnancy and breast feeding
It destroys fetal thyroid
57
How long must a patient who has received radio-iodine treatment wait before conceiving
4 months
58
Radio-iodine is associated with an exacerbation of what
Graves' ophthalmopathy
59
Why is surgery not an ideal treatment for Graves'
It is associated with a higher rate of hypothyroidism or recurrent hyperthyroidism depending on how much of the thyroid is removed
60
What are some of the risks associated with thyroid surgery
Hypoparathyroidism recurrent laryngeal nerve damage laryngeal oedema (due to bleeding int the neck )
61
In what cases is surgery chosen over radio-iodine
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
What is the treatment for mild ophthalmopathy symptoms
Artificial tears during the day and ointments eye shades elevation of the head and neck avoid sleeping on the face
63
What is the treatment for severe ophthalmopathy symptoms
IV methylprednisolone decompression surgery radiotherapy
64
How is subacute and postpartum thyroiditis treated
NSAIDs if mild | Steroids and NSAIDs for moderate or severe
65
How is thyroid hormone resistance characterised by
Reduced responsiveness of the tissues to thyroid hormone
66
What symptoms of thyroid hormone resistance may patients present with
``` Goitre Tachycardia ADHD , learning disability Growth retardation Recurrent ENT infection ```

Lecture Notes - Endocrinology (40 decks)

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