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Year 2 Clinical > Hyper/hypothyroidism > Flashcards

Hyper/hypothyroidism Flashcards

1
Q

Types of hypo/hyperthyroidism?

A

Primary (majority) - problem is intrinsic within the thyroid:
• Non-goitrous
• Goitrous
• Self-limiting

Secondary (rare) - problem is at the level of the pituitary gland OR hypothalamus, e.g: a pituitary tumour that produces excessive TSH (causing hyperthyroidism) OR pituitary gland failure (causing hypothyroidism)

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2
Q

What is the commonest cause of thyroid disease?

A

Autoimmune disease

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3
Q

Thyroid hormones that can be measured?

A

TSH

T4 (free) and T3 (free)

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4
Q

Results in primary hypothyroidism?

A

TSH - high

T4/T3 - low

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5
Q

Results in primary hyperthyroidism?

A

TSH - low

T4/T3 - high

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6
Q

Results in secondary hypothyroidism?

A

TSH - low

T4/T3 - low

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7
Q

Results in secondary hyperthyroidism?

A

TSH - high

T4/T3 - high

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8
Q

Lab results of the different types of hypothyroidism?

A

ADD TABLE

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9
Q

What is hypothyroidism?

A

Variety of abnormalities cause insufficient secretion of thyroid hormones

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10
Q

What is myxoedema?

A

Either refers to:
• Myxoedema coma - severe hypothyroidism
• Pre-tibial myxoedema - accumulation of hydrophilic mucopolysaccharides in the ground substance of the dermis and other tissues (IT OCCURS IN HYPERTHYROIDISM)

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11
Q

Appearance of pre-tibial myxoedema?

A

Doughy induration of the skin classically seen in the shins

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12
Q

When does pre-tibial myxoedema occur?

A

Grave’s disease

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13
Q

Occurrence of hypothyroidism?

A

More common in women and subclinical hypothyroidism is more common than overt

Incidence is higher in Whites and in areas of high iodine uptake

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14
Q

Causes of the different types of primary hypothyroidism?

A

Goitrous:
• Chronic thyroiditis (AKA Hashimoto’s thyroiditis)
• Iodine deficiency

Non-goitrous:
• Congenital development defect
• Atrophic thyroiditis

Self-limiting:
• Withdrawal of suppressive thyroid therapy
• Sub-acute thyroiditis and chronic thyroiditis (transient hypothyroidism)
• Post-partum thyroiditis

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15
Q

What is chronic/Hashimoto’s thyroiditis?

A

Hereditary biosynthetic defect that is maternally transmitted and is an autoimmune disease of the thyroid gland

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16
Q

Causes of iodine deficiency?

A

Can be drug-induced:
• Amiodarone is a common culprit
• Lithium
• IL-2 and IFN-α

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17
Q

What is atrophic thyroiditis?

A

Can be:
• Post-ablative, e.g: due to radioiodine or surgery
• Post-radiation, e.g: for a lymphoma

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18
Q

Hypothalamic causes of secondary hypothyroidism?

A

Congenital

Infection, e.g: encephalitis

Infiltration, e.g: in sarcoidosis

Malignancy, e.g: caraniopharyngioma

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19
Q

Pituitary causes of secondary hypothyroidism?

A 
Panhypopituitarism:
• Trauma
• Infection, e.g: TB, pituitary abscess 
• Infilitration, e.g: sarcoidosis, haemochromatosis, etc
• Neoplasm, e.g: pituitary tumours

Histiocytosis:
• Neoplasms, e.g: pituitary and parapituitary tumours

Pituitary metastatic depositis

Isolated TSH deficiency

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20
Q

What is autoimmune hypothyroidism?

A

AKA Hashimoto’s thyroiditis

Most common cause of hypothyroidism and is autoimmune destruction of the thyroid gland, resulting in reduced thyroid hormone production

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21
Q

Occurrence of autoimmune hypothyroidism?

A

FH of thyroid/autoimmune disease

Females more commonly affected than males

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22
Q

Diagnosis of autoimmune hypothyroidism?

A

Presence of thyroid peroxidase antibodies in the blood

T-cell infiltrate and inflammation on microscopy

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23
Q

Progression of hypothyroidism?

A

Tends to progress over many years from:

  1. Euthyroid
  2. Mild thyroid failure (with T3 and T4 starting to decrease and TSH starting to increase)
  3. Overt hypothyroidism (with T3 and T4 dramatically reduced and TSH increased)
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24
Q

General signs and symptoms of hypothyroidism?

A

Hair - coarse and sparse

Thermogenesis - cold intolerance

Fluid retention - pitting oedema

Face:
• Dull, expressionless face
• Peri-orbital puffiness
• Xanthelasma (due to hyperlipidaemia)

Skin:
• Pale, cool skin that feels doughy
• Vitiligo may be present
• Hypercarotenaemia (increased beta-carotene causes yellow pigmentation of skin)

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25
Q

Cardiac signs and complications of hypothyroidism?

A

Reduced HR

Cardiac dilatation

Pericardial effusion

Worsening of heart failure

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26
Q

Signs of affected metabolic rate in hypothyroidism?

A

Decreased appetite

Weight gain

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27
Q

GI signs of hypothyroidism?

A

Constipation

Megacolon and intestinal obstruction

Ascites

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28
Q

Respiratory signs of hypothyroidism?

A

Deep hoarse voice

Macroglossia (big tongue)

Obstructive sleep apnoea

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29
Q

Neurological/CNS signs and complications of hypothyroidism?

A

Decreased intellectual and motor activities

Depression, psychosis, neuro-psychiatric problems

Muscle stiffness, cramps

Peripheral neuropathy

Prolongation of the tendon jerks

Carpal Tunnel Syndrome

(Cerebellar Ataxia, Encephalopathy)

Decreased Visual Acuity

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30
Q

Gynae/reproduction signs and complications of hypothyroidism?

A

Menorrhagia (heavy periods) and then, later on, oligo- or amenorrhoea

Hyperprolactinaemia (↑ TRH causes ↑ prolactin secretion)

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31
Q

Other Ix for hypothyroidism?

A

Macrocytosis is typical

Vitamin B12 (to rule out a concurrent deficiency)

Elevated creatinine kinase

Increased LDL cholesterol

Hyponatraemia (reduced renal tubular water loss); can occur less commonly due to co-existing cortisol deficiency

Hyperprolactinaemia (increased TRH increases prolactin secretion)

32
Q

Antibodies present in Autoimmune hypothyroidism?

A

Anti-TPO (thyroperoxidase) Ab (best test)

Anti-thyroglobulin Ab

TSH receptor Ab

33
Q

Mx of hypothyroidism?

A

Normal metabolic rate restored GRADUALLY:
• Younger patients - start thyroxine at 50-100μg daily
• Older patients with a PMH of IHD - start thyroxine at 25-50μg daily and adjust every 4 weeks based on response

In pregnancy, dose requirements may increase by 25-50%, due to increase in thyroid binding globulin (TBG)

Preferably taken before breakfast

34
Q

Cautions with thyroixine use?

A

Check TSH 2 months after any dose change

Once stabilised, TSH should be checked once every 12 – 18 months

35
Q

Complications of restoring normal metabolic rate too quickly?

A

May precipitate cardiac arrhythmias; particular care must be taken in elderly patients

36
Q

What is the main treatment in hypothyroidism?

A

Thyroxine (T4)

37
Q

Why is T3 therapy rarely used?

A

Has a short 1/2-life

38
Q

Monitoring of therapy in primary hypothyroidism?

A

TSH reflects tissue thyroid hormone actions; TSH is an index of therapeutic success and potential toxicity

39
Q

Monitoring of therapy in secondary hypothyroidism?

A

TSH is not as useful (remains lows if T4 therapy is commenced)

Instead, T4 is used to monitor treatment

40
Q

Occurrence of myxoedema coma?

A

Tends to affect elderly women with long-standing but frequently unrecognized OR untreated hypothyroidism

Mortality is high

41
Q

Investigation findings in myxoedema coma?

A 
ECG:
• Bradycardia
• Low voltage complexes
• Varying degrees of heart block
• T wave inversion
• Prolongation of the QT interval

Type 2 respiratory failure (hypoxia, hypercarbia, respiratory acidosis)

Co-existing adrenal failure is present in 10% of patients

42
Q

Treatment of myxoedema coma?

A

Intensive care (ABC)

Passively rewarm (aim for a slow in body temp)

Monitor for arrhythmias, BP, CVP, oxygenation, urine output, blood glucose levels, electrolytes

Fluids OR fluid restriction

Broad spectrum antibiotics

Thyroxine cautious; administer hydrocortisone

43
Q

Cardiac signs of hyperthyroidism?

A

Palpitations

Increased risk of AF

Cardiac failure (rare), due to increased rate and force of contraction of the heart

44
Q

Sympathetic signs of hyperthyroidism?

A

Tremor and sweating

45
Q

CNS signs of hyperthyroidism?

A

Anxiety, nervousness, irritability, sleep disturbance

46
Q

GI signs of hyperthyroidism?

A

Frequent, loss bowel movements (diarrhoea)

47
Q

Visual signs of hyperthyroidism?

A

Lid retraction

Double vision

Eyes that bulge out or protrude (in patients with Grave’s disease)

48
Q

Hair and nail signs in hyperthyroidism?

A

Brittle and thinning hair

Rapid fingernail growth

49
Q

Reproductive signs in hyperthyroidism?

A

Menstrual cycle changes, inc. lighter bleeding and less frequent periods

50
Q

Muscle signs in hyperthyroidism?

A

Muscle weakness, esp. thighs and upper arms

51
Q

Metabolic signs of hyperthyroidism?

A

Weight loss despite increased appetitie

52
Q

Thermogenesis signs of hyperthyroidism?

A

Intolerance of heat

53
Q

Causes of hyperthyroidism?

A

Autoimmune:
• Graves disease

Nodular thyroid:
• Multi-nodular goitre
• Toxic nodule (adenoma)

Thyroiditis (inflammation):
• Sub-acute
• Post-partum

54
Q

Rarer causes of hyperthyroidism?

A

Iodine:
• From medications, e.g: amiodarone and thyroxine
• Supplements like kelp

Other medications, e.g: lithium, amiodarone and thyroxine

55
Q

Occurrence of Grave’s disease?

A

More common in women and in younger people (20-50 years)

May have a +ve FH

May be related to high iodine intake, smoking

56
Q

Ix results for Grave’s disease?

A

High T3/T4 and low TSH

Ab +ve (TSH receptor antibody is best)

Smooth symmetrical goitre shows with US and scintigraphy (shows symmetrical uptake)

57
Q

Antibodies for Graves’s disease?

A

TSH-receptor Ab (best and more present than in autoimmune hypothyroidism)

Anti-thyroglobulin Ab

Anti-TPO Ab (2nd best)

58
Q

Natural progression of Grave’s disease?

A

Varying course over 1 year but at 18 months:
• 50% will burn out
• 50% will relapse

59
Q

Eye signs of Grave’s disease?

A

Grave’s opthalmopathy has signs of:
• Lid retraction
• Lid lag (not specific to Grave’s but occurs in hyperthyroidism)
• Chemosis (redness)
• Proptosis
• Visual loss (encroachment on optic nerve)
• Diplopia

60
Q

Treatment of Grave’s opthalmopathy?

A

Depends on severity:

  1. Lubricants
  2. Decompression Surgery
  3. Radiotherapy
  4. Corrective Surgery

Smoking cessation

61
Q

Presentation of nodular thyroid disease?

A

Occurs in older patients and has a more insidious onset

Gland may feel nodular

62
Q

Ix results in modular thyroid disease?

A

High T3/T4 and low TSH

Ab -ve

Asymmetrical goitre shows with US and scintigraphy

63
Q

What is thyroid storm?

A

Severe hyperthyroidism assoc. with:
• Respiratory and cardiac collapse
• Hyperthermia
• Exaggerated reflexes

There may be an assoc. underlying infection

64
Q

Treatment of thyroid storm?

A 
EMERGENCY (ABC):
• Lugols iodine
• Glucocorticoids (calm systemic inflammatory response)
• PTU
• β-blockers
• Fluids

Must monitor frequently

It may require ventilation

65
Q

Treatment options for hyperthyroidism?

A

• Carbimazole
• Propylthiouracil (preferred in pregnancy)
In Graves, start at a high dose and reduced over 12-18 months before stopping (50% chance of relapsing)

  • Can give β-blockers for symptomatic treatment
  • Radio-iodine
  • Surgery (thyroidectomy)
66
Q

Side effect of both carbimazole and propylthiouracil?

A

Risk of agranulocytosis; advise them to see doctor if they develop a febrile illness

67
Q

Precautions with radio-iodine use?

A

Patient becomes slightly radioactive so:
• Avoid close prolonged contact with young children/pregnant women
• Do not share a bed for a certain no. of weeks/days
• Avoid pregnancy for 6 months and ensure not pregnant

68
Q

Risk with radio-iodine use?

A

High risk of hypothyroidism (esp. in Grave’s)

69
Q

Risks with surgery?

A

Scar

Surgical/anaesthetic risks, inc. recurrent laryngeal nerve palsy

Hypothyroidism

Hypo-parathyroidism

70
Q

Types of thyroiditis?

A

Grave’s
Hashimoto’s
DeQuervain’s/subacute (viral)
Post-partum
Drug-induced (amiodarone, lithium) and radiation thyroiditis
Acute thyroiditis/suppurative (bacterial)

71
Q

Presentation of sub-acute thyroiditis/De Quervain’s?

A

More common in females than males; tends to be 20-50 years

As it may be viral triggered it may be assoc. with a sore throat/fever/other viral symptoms

72
Q

Treatment of sub-acute thyroiditis/DeQuervains’s?

A

Usually self-limiting (over a few months)

73
Q

Ix results in sub-acute thyroiditis/DeQuervain’s?

A

T4 is high in early stages and low in late before becoming normal

TSH is low in early stages, high in late before becoming normal

Scintigraphy scan shows LOW UPTAKE

74
Q

Occurrence of amiodarone-induced thyroid dysfunction?

A

Can occur in up to 1/2 of patients on the drug

Some develop hypothyroidism (amiodarone-induced thyrotoxicosis occurs more frequently in areas with low iodine intake)

Thyrotoxicosis can occur but less commonly (amiodarone-induced hypothyroidism occurs more frequently in areas with high iodine intake)

75
Q

Ix results in SUB-CLINICAL hyperthyroidism?

A

There is a mildly overactive thyroid:
• TSH low
• T4/T3 normal

76
Q

Ix results in SUB-CLINICAL hypothyroidism?

A

There is a failing thyroid gland:
• TSH high
• T4/T3 normal

Year 2 Clinical (119 decks)

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