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Year 2 Clinical > Hyper/hypothyroidism > Flashcards

Hyper/hypothyroidism Flashcards

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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
Cardiac signs and complications of hypothyroidism?
Reduced HR Cardiac dilatation Pericardial effusion Worsening of heart failure
26
Signs of affected metabolic rate in hypothyroidism?
Decreased appetite Weight gain
27
GI signs of hypothyroidism?
Constipation Megacolon and intestinal obstruction Ascites
28
Respiratory signs of hypothyroidism?
Deep hoarse voice Macroglossia (big tongue) Obstructive sleep apnoea
29
Neurological/CNS signs and complications of hypothyroidism?
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
30
Gynae/reproduction signs and complications of hypothyroidism?
Menorrhagia (heavy periods) and then, later on, oligo- or amenorrhoea Hyperprolactinaemia (↑ TRH causes ↑ prolactin secretion)
31
Other Ix for hypothyroidism?
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
Antibodies present in Autoimmune hypothyroidism?
Anti-TPO (thyroperoxidase) Ab (best test) Anti-thyroglobulin Ab TSH receptor Ab
33
Mx of hypothyroidism?
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
Cautions with thyroixine use?
Check TSH 2 months after any dose change Once stabilised, TSH should be checked once every 12 – 18 months
35
Complications of restoring normal metabolic rate too quickly?
May precipitate cardiac arrhythmias; particular care must be taken in elderly patients
36
What is the main treatment in hypothyroidism?
Thyroxine (T4)
37
Why is T3 therapy rarely used?
Has a short 1/2-life
38
Monitoring of therapy in primary hypothyroidism?
TSH reflects tissue thyroid hormone actions; TSH is an index of therapeutic success and potential toxicity
39
Monitoring of therapy in secondary hypothyroidism?
TSH is not as useful (remains lows if T4 therapy is commenced) Instead, T4 is used to monitor treatment
40
Occurrence of myxoedema coma?
Tends to affect elderly women with long-standing but frequently unrecognized OR untreated hypothyroidism Mortality is high
41
Investigation findings in myxoedema coma?
``` 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
Treatment of myxoedema coma?
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
Cardiac signs of hyperthyroidism?
Palpitations Increased risk of AF Cardiac failure (rare), due to increased rate and force of contraction of the heart
44
Sympathetic signs of hyperthyroidism?
Tremor and sweating
45
CNS signs of hyperthyroidism?
Anxiety, nervousness, irritability, sleep disturbance
46
GI signs of hyperthyroidism?
Frequent, loss bowel movements (diarrhoea)
47
Visual signs of hyperthyroidism?
Lid retraction Double vision Eyes that bulge out or protrude (in patients with Grave's disease)
48
Hair and nail signs in hyperthyroidism?
Brittle and thinning hair Rapid fingernail growth
49
Reproductive signs in hyperthyroidism?
Menstrual cycle changes, inc. lighter bleeding and less frequent periods
50
Muscle signs in hyperthyroidism?
Muscle weakness, esp. thighs and upper arms
51
Metabolic signs of hyperthyroidism?
Weight loss despite increased appetitie
52
Thermogenesis signs of hyperthyroidism?
Intolerance of heat
53
Causes of hyperthyroidism?
Autoimmune: • Graves disease Nodular thyroid: • Multi-nodular goitre • Toxic nodule (adenoma) Thyroiditis (inflammation): • Sub-acute • Post-partum
54
Rarer causes of hyperthyroidism?
Iodine: • From medications, e.g: amiodarone and thyroxine • Supplements like kelp Other medications, e.g: lithium, amiodarone and thyroxine
55
Occurrence of Grave's disease?
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
Ix results for Grave's disease?
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
Antibodies for Graves's disease?
TSH-receptor Ab (best and more present than in autoimmune hypothyroidism) Anti-thyroglobulin Ab Anti-TPO Ab (2nd best)
58
Natural progression of Grave's disease?
Varying course over 1 year but at 18 months: • 50% will burn out • 50% will relapse
59
Eye signs of Grave's disease?
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
Treatment of Grave's opthalmopathy?
Depends on severity: 1. Lubricants 2. Decompression Surgery 3. Radiotherapy 4. Corrective Surgery Smoking cessation
61
Presentation of nodular thyroid disease?
Occurs in older patients and has a more insidious onset Gland may feel nodular
62
Ix results in modular thyroid disease?
High T3/T4 and low TSH Ab -ve Asymmetrical goitre shows with US and scintigraphy
63
What is thyroid storm?
Severe hyperthyroidism assoc. with: • Respiratory and cardiac collapse • Hyperthermia • Exaggerated reflexes There may be an assoc. underlying infection
64
Treatment of thyroid storm?
``` EMERGENCY (ABC): • Lugols iodine • Glucocorticoids (calm systemic inflammatory response) • PTU • β-blockers • Fluids ``` Must monitor frequently It may require ventilation
65
Treatment options for hyperthyroidism?
• 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
Side effect of both carbimazole and propylthiouracil?
Risk of agranulocytosis; advise them to see doctor if they develop a febrile illness
67
Precautions with radio-iodine use?
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
Risk with radio-iodine use?
High risk of hypothyroidism (esp. in Grave's)
69
Risks with surgery?
Scar Surgical/anaesthetic risks, inc. recurrent laryngeal nerve palsy Hypothyroidism Hypo-parathyroidism
70
Types of thyroiditis?
Grave's Hashimoto's DeQuervain's/subacute (viral) Post-partum Drug-induced (amiodarone, lithium) and radiation thyroiditis Acute thyroiditis/suppurative (bacterial)
71
Presentation of sub-acute thyroiditis/De Quervain's?
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
Treatment of sub-acute thyroiditis/DeQuervains's?
Usually self-limiting (over a few months)
73
Ix results in sub-acute thyroiditis/DeQuervain's?
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
Occurrence of amiodarone-induced thyroid dysfunction?
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
Ix results in SUB-CLINICAL hyperthyroidism?
There is a mildly overactive thyroid: • TSH low • T4/T3 normal
76
Ix results in SUB-CLINICAL hypothyroidism?
There is a failing thyroid gland: • TSH high • T4/T3 normal

Year 2 Clinical (119 decks)

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