Thyroid - Hypothyroidism Flashcards

1
Q

What will TFTs show in primary hypothyroidism?

A

TSH- high

T3/T4- low

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2
Q

What will TFTs show in secondary hypothyroidism?

A

TSH- low or normal

T3/T4- low

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3
Q

What is the definition of hypothyroidism?

A

Any disorder that results in insufficient secretion of thyroid hormones from the thyroid gland

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4
Q

What is myxoedema coma?

A

A hypothyroid emergency

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5
Q

In general, hypothyroidism is most common in which sex and of which age group?

A

Females, 65+

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6
Q

Hypothyroidism has a higher incidence in which race?

A

White populations

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7
Q

What environmental factor causes a higher incidence of hypothyroidism?

A

Areas of iodine deficiency

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8
Q

What are 5 causes of goitrous, primary hypothyroidism?

A
  • Hashimoto’s thyroiditis
  • Iodine deficiency
  • Drug induced
  • Maternally transmitted
  • Hereditary defects
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9
Q

What 2 drugs have a big effect on thyroid function?

A

Amiodarone and lithium

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10
Q

How is hypothyroidism maternally transmitted?

A

If the mother is on anti-thyroid drugs

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11
Q

Is Hashimoto’s thyroiditis always goitrous?

A

No

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12
Q

What are 4 causes of non-goitrous, primary hypothyroidism?

A
  • Hashimoto’s thyroiditis
  • Post-ablative therapy
  • Post-radiotherapy
  • Congenital defects
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13
Q

What are 3 examples of self-limiting hypothyroidism?

A
  • Following withdrawal of anti-thyroid drugs
  • Subacute thyroiditis
  • Post-partum thyroiditis
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14
Q

What causes secondary hypothyroidism?

A

Hypothalamic or pituitary disease

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15
Q

What are 6 causes of hypothalamic-pituitary disease?

A
  • Infiltrative disease
  • Malignancy
  • Infection
  • Cranial radiotherapy
  • Congenital disorders
  • Trauma
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16
Q

What effects can hypothyroidism have on the hair and skin?

A
  • Vitiligo
  • Coarse, sparse hair
  • Periorbital puffiness
  • Pale, cool, doughy skin
  • Hypercarotenaemia
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17
Q

What effect does hypothyroidism have on thermogenesis?

A

Cold intolerance

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18
Q

What clinical sign appears in hypothyroidism as a result of abnormal fluid balance?

A

Pitting oedema

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19
Q

What effects can hypothyroidism have on the CV system?

A
  • Decreased HR
  • Cardiac dilatation
  • Pericardial effusion
  • Worsening of heart failure
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20
Q

What metabolic effects does hypothyroidism have?

A
  • Hyperlipidaemia

- Weight gain and decreased appetite

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21
Q

What GI effects can hypothyroidism cause?

A
  • Constipation
  • Intestinal obstruction
  • Ascites
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22
Q

What respiratory effects can hypothyroidism cause?

A
  • Deep, hoarse voice
  • Macroglossia
  • Sleep apnoea
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23
Q

What neurological/CNS effects can hypothyroidism have?

A
  • Depression, psychosis
  • Muscle stiffness, cramps
  • Peripheral neuropathy
  • Decreased visual activity
24
Q

What reproductive effects can hypothyroidism have?

A
  • Menorrhagia
  • Oligo/amenorrhoea (later)
  • Hyperprolactinaemia
25
Q

Hypothyroidism causes macrocytosis. What is this and what test will show it?

A

Enlarged red blood cells, increased MCV

26
Q

What does hypothyroidism do to creatinine kinase?

A

Increases it

27
Q

What does hypothyroidism do to LDL cholesterol?

A

Increases it

28
Q

What effect does hypothyroidism have on sodium concentration and why?

A

Hyponatraemia- decreases renal tubular water loss

29
Q

Why does hypothyroidism cause hyperprolactinaemia?

A

Increased TRH increased PRL secretion

30
Q

What type of disease is Hashimoto’s thyroiditis?

A

Autoimmune

31
Q

What are the two main antibodies involved in Hashimoto’s thyroiditis? Which is the major one?

A

Anti-thyroglobulin (60%) and anti-thyroperoxidase (95%)

32
Q

Is TRAb ever present in Hashimoto’s thyroiditis?

A

Yes (10-20%)

33
Q

Autoantibodies in Hashimoto’s thyroiditis cause antibody mediated, cell dependent cytotoxicity via what cell?

A

CD8+ T cells

34
Q

How does cytokine mediated cell death occur in Hashimoto’s thyroiditis?

A

Gamma interferon from T cell activation recruits macrophages

35
Q

What sex and age group is Hashimoto’s most common in?

A

Females, 45-60

36
Q

What may precede Hashimoto’s thyroiditis?

A

Transient hyperfunction (hashitoxicosis)

37
Q

What type of goitre will Hashimoto’s usually cause?

A

Diffuse, firm, painless

38
Q

There is an increased risk of what type of cancer in the gland affected by Hashimoto’s thyroiditis?

A

B cell Non-Hodgkins Lymphoma

39
Q

What other autoimmune conditions are most commonly affected with autoimmune thyroid disease?

A

Addison’s disease, pernicious anaemia, Type 1 diabetes

40
Q

What is the main treatment of hypothyroidism?

A

Levothyroxine

41
Q

What is the main risk of levothyroxine increasing metabolic rate?

A

Cardiac arrhythmias

42
Q

What is the normal dosage of Levothyroxine?

A

50-100 macrograms daily

43
Q

When should the normal dosage of levothyroxine be changed and what to?

A

In the elderly or those with ischaemic heart disease it should be 25-50 macro grams initially and adjusted every 4 weeks depending on response

44
Q

Once TSH is stabilised with Levothyroxine, how often should levels be checked?

A

Every 12-18 months

45
Q

Is there proven benefit of T3/4 combined treatment?

A

No

46
Q

When in the day is levothyroxine preferably taken?

A

Before breakfast

47
Q

What happens to the dose of levothyroxine in pregnancy and why?

A

It increases (usually by 25-50%) since pregnancy increases thyroid binding globulin

48
Q

What drugs interfere with Levothyroxine?

A

Ca++ and iron tablets and PPIs

49
Q

Who is most commonly affected by myxoedema coma?

A

Elderly females with longstanding but unrecognised or untreated hypothyroidism

50
Q

Why is the mortality rate of myxoedema coma so high?

A

Co-morbidities

51
Q

What 4 things may an ECG of someone with myxoedema coma show?

A
  • Bradycardia
  • Varying degrees of heart failure
  • T wave inversion
  • Prolonged QT interval
52
Q

What type of respiratory failure will occur in myxoedema coma? What are the features of this?

A

Type 2- hypoxia, hypercapnia, respiratory acidosis

53
Q

Co-existing failure of what is present in 10% of myxoedema coma patients?

A

Adrenals

54
Q

How should patients with myxoedema coma be treated?

A
  • ABCDE, intensive care

- Passively rewarmed

55
Q

What is the major thing that should be monitored for in myxoedema coma?

A

Arrhythmias

56
Q

What 4 things should be monitored in myxoedema come?

A

Oxygenation, urine output, fluid balance, blood sugars

57
Q

What drugs should myxoedema coma patients be given?

A

Broad spectrum antibiotics and thyroxine (cautiously)