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Endocrine > Hypo/Hyperthyroidism > Flashcards

Hypo/Hyperthyroidism Flashcards

1
Q

What is a primary thyroid disease?

A

Disease affecting thyroid gland itself, can occur with goitre (goitrous) or without (non-goitrous), most commonly autoimmune

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2
Q

What is a secondary thyroid disease?

A

Hypothalamic or pituitary disease, no thyroid gland pathology

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3
Q

What is the other name for thyroid stimulating hormone (TSH)?

A

Thyrotropin = reflects tissue thyroid hormone action

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4
Q

What releases TSH?

A

Released by thyrotroph cells in anterior pituitary in response to thyrotropin releasing hormone (TRH)

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5
Q

What are the blood abnormalities for primary hypothyroidism and hyperthyroidism?

A 
Hypo = free T3/4 low, TSH high
Hyper = free T3/4 high, TSH low
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6
Q

What are the blood abnormalities for secondary hypothyroidism and hyperthyroidism?

A 
Hypo = free T3/4 low, TSH low (or normal)
Hyper = free T3/4 high, TSH high (or normal)
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7
Q

What is myxoedema?

A

Severe hypothyroidism = medical emergency

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8
Q

What is pretibial myxoedema?

A

Rare clinical sign of Grave’s disease, which causes hyperthyroidism

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9
Q

What are some features of hypothyroidism?

A

Increased TSH in 7.5% of females and 2.5% of males >65, incidence higher in white populations and areas of high iodine intake

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10
Q

What are some causes of primary goitrous hypothyroidism?

A

Chronic thyroiditis, iodine deficiency, drug induced, maternally transmitted, hereditary biosynthetic defects

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11
Q

What are some causes of primary non-goitrous hypothyroidism?

A

Atrophic thyroiditis, post-ablative therapy, post-radiotherapy, congenital developmental defect

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12
Q

What are some features of Hashimoto’s thyroiditis?

A

Most common causes of hypothyroidism in Western world, often family history, more common in females

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13
Q

What occurs in Hashimoto’s thyroiditis?

A

Autoimmune destruction of thyroid gland and reduced thyroid hormone production

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14
Q

What is Hashimoto’s thyroiditis characterised by?

A

Antibodies against thyroid peroxidase (TPO), and T cell infiltrate and inflammation microscopically

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15
Q

What are some general symptoms of hypothyroidism?

A

Coarse sparse hair, dull expressionless face, periorbital puffiness, doughy pale cool skin, vitiligo, hypercarotenaemia, cold intolerance, hyperlipidaemia

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16
Q

What are some cardiac and GI symptoms of hypothyroidism?

A 
Cardiac = slow heart rate, cardiac dilation, pericardial effusion
GI = weight gain, decreased appetite, constipation
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17
Q

What are some CNS symptoms of hypothyroidism?

A

Depression, psychosis, muscle stiffness, peripheral neuropathy, carpal tunnel syndrome

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18
Q

What are some reproductive symptoms of hypothyroidism?

A

Menorrhagia, oligo/amenorrhoea, hyperprolactinaemia

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19
Q

How are primary causes of hypothyroidism investigated?

A 
Increased TSH and decreased T3/4
Increased MCV (microcytosis), increased CK, increased LDL, hyponatraemia, hyperprolactinaemia
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20
Q

What antibodies are linked to primary hypothyroidism?

A

Anti-TPO = 95%
Anti-Tg = 60%
TSH receptor = 10-20%

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21
Q

Why does normal metabolic rate need to be restored gradually in hypothyroidism?

A

Doing it too quickly may cause cardiac arrhythmias

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22
Q

How are young patients with hypothyroidism treated?

A

Start levothyroxine at 50-100 micrograms daily

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23
Q

How are elderly patients with hypothyroidism treated?

A

Levothyroxine at 25-50 micrograms daily = adjusted every 4 weeks according to response

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24
Q

How often should TSH be checked in patients with hypothyroidism?

A

Check 2 months after any dose change, once stabilised check every 12-18 months
TSH unreliable in secondary causes

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25
Q

How is T3 used to treat hypothyroidism?

A

Very rarely used = more potent than T4 therapy, effects develop within a few hours and disappear within 24-48hrs of stopping

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26
Q

How is typically affected by myxoedema comas?

A

Elderly women with long standing but frequently untreated hypothyroidism

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27
Q

Are myxoedema comas a medical emergency?

A

Yes = mortality up to 60%, type 2 respiratory failure occurs , treated with ABCDE approach, antibiotics and hydrocortisone

28
Q

What are the ECG features of myxoedema comas?

A

Bradycardia, low voltage complexes, heart block, T wave inversion, prolonged QT

29
Q

What does thyrotoxicosis describe?

A

The clinical state arising when tissues are exposed to excess thyroid hormone

30
Q

What does hyperthyroidism refer to?

A

Refers specifically to conditions in which overactivity of the thyroid gland leads to thyrotoxicosis

31
Q

What are the cardiac and CNS symptoms of thyrotoxicosis?

A 
Cardiac = palpitations, AF, cardiac failure (rare), tremor
CNS = anxiety, nervousness, irritability, sleep disturbance, muscle weakness, sweating
32
Q

What are some general symptoms of thyrotoxicosis?

A

Diarrhoea, weight loss, lighter less frequent periods, eyelid retraction, double vision, proptosis (specific to Grave’s)

33
Q

What are some causes of thyrotoxicosis that are associated with hyperthyroidism?

A

Excessive stimulation = Grave’s, Hashitoxicosis, thyrotropinoma (very rare), choriocarcinoma
Toxic solitary nodule, toxic multinodular goitre

34
Q

What are some causes of thyrotoxicosis that aren’t associated with hyperthyroidism?

A

Subacute thyroiditis, postpartum thyroiditis, drug-induced thyroiditis, over treatment with levothyroxine, thyrotoxicosis factitial, metastatic thyroid carcinoma, struma ovarii

35
Q

What are some features of Grave’s disease?

A

Common in young (20-50 years), more common in women, influenced by smoking, associated with osteoporosis

36
Q

What do the investigations for Grave’s disease show?

A

Decreased TSH and increased T3/4
Hypercalcaemia and increased alkaline phosphatase
Leucopenia
TSH receptor antibody (TRAb, 70-100%), anti-TPO antibody (70-80%)

37
Q

What are some signs of Grave’s disease?

A

Pretibial myxoedema, thyroid acropachy, thyroid bruit (associated with large goitres, heard over thyroid)

38
Q

What are some features of Grave’s eye disease?

A

Occurs in 20%, associated with smoking, TRAb driven, can precede Grave’s diagnosis, can be unilateral, usually mild but can be sight-threatening, mild treated topically, severe may need surgery or steroids

39
Q

What are some features of nodular thyroid disease?

A

Older patients, more insidious onsets, thyroid may feel nodular, asymmetric goitre

40
Q

What are some investigations for nodular thyroid disease?

A

Increased fT4/3, decreased TSH, antibody negative, high uptake on scintigraphy, USS

41
Q

What is thyroid storm?

A

Medical emergency = severe hyperthyroidism

Respiratory/cardiac collapse, hyperthermia, exaggerated reflexes

42
Q

How is thyroid storm treated?

A

May require mechanical ventilation

Lugol’s iodine or glucocorticoids

43
Q

What patients suffer from thyroid storm?

A

Typically hyperthyroid patients with acute infection/illness or recent thyroid surgery

44
Q

What are some treatments for hyperthyroidism?

A

Anti-thyroid drugs (ATDs), beta blockers, radioiodine, thyroidectomy

45
Q

How do anti-thyroid drugs work?

A

Inhibit TPO thereby blocking thyroid hormone synthesis

46
Q

What are some examples of anti-thyroid drugs?

A

Carbimazole, propylthiouracil (PTU)

47
Q

What are some features of carbimazole?

A

First line drug, once daily, risk of aplasia cutis in early pregnancy

48
Q

What are some features of propylthiouracil?

A

Only first line in the first trimester of pregnancy, twice daily, inhibits DIO1, 10x less potent than carbimazole

49
Q

How are anti-thyroid drugs used to treat Grave’s disease?

A

Dose titration (12-18 months) or block and replace (6 months), 50% relapse

50
Q

What are the side effects of anti-thyroid drugs?

A

Generally well tolerated. 1-5% develop allergic-type reactions, fulminant hepatic failure and cholestatic jaundice with PTU use, agranulocytosis

51
Q

What are some features of agranulocytosis?

A

ATD cant be used again, highest risk in first six weeks

52
Q

How are beta blockers used to treat hyperthyroidism?

A

Useful for immediate symptom relief, reduce activity of sympathetic nervous system, propranolol is drug of choice (also blocks DIO1), caution in asthmatics

53
Q

How is radioiodine used to treat hyperthyroidism?

A

1st choice treatment for relapsed Grave’s and nodular thyroid disease, high risk of hypothyroidism when used in Grave’s disease

54
Q

When is radioiodine contraindicated?

A

Pregnancy

Active thyroid eye disease = can be used with steroid cover

55
Q

When is a thyroidectomy indicated, and what are the risks?

A

When radioiodine is contraindicated

Risks = recurrent laryngeal nerve palsy, hypothyroidism, hypoparathyroidism

56
Q

What is thyroiditis?

A

Inflammation of thyroid = Hashimoto’s, DeQuervain’s/subacute, postpartum, drug-induced (amiodarone), acute suppressive thyroiditis

57
Q

What are some features of subacute thyroiditis?

A

More common in females, age 20-50 years, may be triggered by viral infection, usually self-limiting

58
Q

What are the symptoms of subacute thyroiditis?

A

Neck tenderness, fever, other viral symptoms

Scintigraphy shows slow uptake

59
Q

How does amiodarone cause thyroiditis?

A

TFTs abnormal in 50% = inhibition of DIO1 (increased fT4, decreased fT3, normal TSH)

60
Q

What are the features of the hypothyroidism and hyperthyroidism that can occur in amiodarone-associated thyroiditis?

A 
Hypo = occurs in 13%, associated with iodine rich areas
Hyper = occurs in 2%, associated with iodine deficient areas, type 1 (similar to Grave's), type 2 (destructive) or mixed
61
Q

What is the characteristic of subclinical thyroid disease?

A

Abnormal TSH with normal thyroid hormone levels

62
Q

What are the features of subclinical hypothyroidism?

A

Increased TSH, risk of progression to overt hypothyroidism, higher risk if strongly TPO antibody positive, treat is TSH >10, always treat in pregnancy

63
Q

What are the features of subclinical hyperthyroidism?

A

Decreased TSH, risk of progression to overt hyperthyroidism, often seen in multinodular goitre

64
Q

What is the other name for non-thyroidal illness?

A

Sick euthyroid syndrome = refers to impact of intercurrent illness on the HPT axis

65
Q

What patients typically suffer from non-thyroidal illness?

A

Unwell hospitalised patients

66
Q

What are the features of non-thyroidal illness?

A

TSH typically suppressed initially then rises during recovery = avoid checking TFTs in unwell patients unless clinical suspicion of thyroid disease

Endocrine (42 decks)

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