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Endocrine > Hypothyroidism/Thyroiditis > Flashcards

Hypothyroidism/Thyroiditis Flashcards

1
Q

slide 1-5

A

…

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2
Q

describe the hypothalamic pituitary thyroid axix (HPT axis)

A

hypothalamus produces TRH which stimulates anterior pituitary to produce ……..

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3
Q

how are thyroid hormones affected in primary hypothyroidism?

A

Free T3 and T4 = low

TSH = high (to try and compensate for the lack of T3 and T4 production)

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4
Q

how are thyroid hormones affected in primary hyperthyroidism?

A

free T3 and T4 = high

TSH = low (to try and reduce production of T3 and T4)

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5
Q

how are thyroid hormones affected in secondary hypothyroidism?

A

free T3 and T4 = low
TSH = low or normal (usually some condition affecting the anterior pituitary so less signalling to thyroid to produce T3 and T4)

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6
Q

how are thyroid hormones affected in secondary hyperthyroidism?

A

free T3 and T4 = high

TSH = high or normal (problem in anterior pituitary e.g TSH secreting tumour, loss of negative feedback response etc)

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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 graves disease

- autoimmune thyroid disease resulting in hyperthyroidism

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9
Q

in what populations is hypothyroidism more common?

A

white populations
women
older
areas of high iodine intake

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10
Q

what are the 3 causes of primary hypothyroidism?

A

goitorous
non-goitorous
self-limiting

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11
Q

examples of goitrous hypothyroidism?

A 
chronic thyroiditis (hashimotos)
iodine deficiency
drug induced
maternally transmitted
hereditary defects
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12
Q

causes of non-goitrous hypothyroidism?

A

atrophic thyroiditis
post ablative therapy (surgery, radioiodine)
radiotherapy
congenital defect

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13
Q

causes of self limitng hypothyroidism?

A

withdrawal of antithyroid drugs

post partum

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14
Q

what can cause secondary hypothyroidism?

A 
infiltrative
infection
malignancy
trauma
congenital
cranial radiotherapy
drug induced
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15
Q

what is hashimotos thyroiditis?

A

autoimmune hypothyroidism
- most common cause of hypothyroidism
autoimmune destruction of thyroid gland and reduced thyroid hormone production

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16
Q

what are the characteristics of hashimotos?

A

family history of autoimmune disease
antibodies against thyroid peroxidase (TPO)
t cell infiltrate and inflammation microscopically

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17
Q

what are the 3 stages in progression of thyroid disease?

A

euthyroid (normal)
mild thyroid failure
overt hypothyroidism

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18
Q

what are the clinical features of hypothyroidism?

A 
coarse, sparse hair
dull, expressionless face
puffy face
pale, cool skin (doughy to touch)
vitiligo
hypercarotenaemia
cold intolerance
fluid retention (pitting oedema)
hyperlipidaemia
decreased apetitie
weight gain
constipation
megacolon and intestinal obstruction
ascites
deep hoarse voice
macroglossia
sleep apnoea
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19
Q

what are the cardiac features of hypothyroidism?

A 
slow HR
cardiac dilatation
pericardial effusion
worsening of heart failure
hyperlipidaemia
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20
Q

neurological features of hypothyroidism?

A 
decreased intellectual and motor activities
depression, psychosis
muscle stiffness, cramos
peripheral neuropathy
prolonged tendon jerks
carpal tunnel
decreased visual acuity
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21
Q

reproductive features of hypothyroidism?

A

menorrhagia
later oligo or amenorrhoea
hyperprolactinaemia

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22
Q

lab investigations for primary hypothyroidism?

A 
increased TSH and low T3/4
increased MCV
raised LDL
raised CK
low sodium
hyperprolactinaemia
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23
Q

graves disease autoantibodies?

A 
anti TPO (70-80%)
anti thyroglobulin (30-50%)
TSH receptor antibody (70-100%)
24
Q

autoantibodies in autoimmune hypothyroidism?

A

anti TPO (95%)
anti-thyroglobulin (60%)
TSH receptor antibody (10-20%)

25
Q

how is hypothyroidism managed?

A

restore metabolic rate slowly to prevent arrhythmia
younger = levothyroxine 50-100 micrograms daily
elderly = 25-50 micrograms daily
check TSH 2 months after dose change then every 12-18 months once stabilised

26
Q

what is levothyroxine and how is it used?

A

T4
taken before breakfast
no benefit of combining with T3
may need to increase dose by 20-25% in pregnancy (due to increased TBG)

27
Q

who does myxoedema coma usually affect?

A

elderly women with long standing untreated hypothyroidism

28
Q

what are the features of myxoedema coma?

A

bradycardia
type 2 resp failure
co-existing adrenal failure (in 10%)
reduced consciousness

29
Q

how is myxoedema coma managed?

A 
ICU
slowly warm up patient
monitor heart, urine, fluids, BP, BG and sats
antibiotics
thyroxine cautiously (hydrocortisone)
30
Q

thyrotoxicosis vs hyperthyroidism?

A 
thyrotoxicosis = any state arising from tissues being exposed to excess thyroid hormone (can be from medication)
hyperthyroidism = specific to overactivity of thyroid hormone leading to thyrotoxicosis
31
Q

signs of hyperthyroidism/thyrotoxicosis?

A 
palpitations
AF
cardiac failure (rare)
tremor
sweating
anxiety, nervous, irritable, sleep disturbance
32
Q

symptoms of thyrotoxicosis?

A 
loose bowels
lid retraction
double vision
proptosis
brittle, thin hair
rapid fingernail growth
light/less frequent periods
muscle weakness
weight loss despite increased appetite
intolerance to heat
33
Q

causes of hyperthyroidism?

A 
excessive thyroid stimulation
- graves
- thyrotropinoma
- thyroid cancer
- choriocarcinoma
thyroid nodules with autonomous function
- toxic solitary nodule
- toxic multinodular goitre
34
Q

causes of thyrotoxicosis (not associated with hyperthyroidism)?

A 
thyroid inflammation 
- subacute (de quervains) thyroiditis
- post partum thyroiditis
- drug induced (amiodarone)
exogenous thyroid hormones
- over treatment with levothyroxine
- thyrotoxicosis factitial
ectopic thyroid tissue
- metastatic thyroid carcinoma
- struma ovarii
35
Q

risk factors for graves disease?

A

younger - 20-50 yrs
sisters and children of women with graves disease
smoking
interacting susceptibility genes and environmental factors

36
Q

lab investigations in graves disease?

A 
reduced TSH and increased T3/4
hypercalcaemia 
raised alk phosphate
leucopenia (low WCC)
TSH receptor antibody (TRAb)
- diagnostic if present so imaging not needed
37
Q

what clinical signs are specific to graves disease?

A

pretibial myxoedema
thyroid acropachy (clubbing with thyrotoxicosis)
thyroid bruits (assoc with very large goitres)
graves eye disease

38
Q

what is graves eye disease?

A

TRAb driven pathology of the eye seen in graves - can affect one or both eyes
also called thyroid eye disease (TED) and graves opthalmopathy (GO)
can be sight threatening
often causes protrusion of eyes

39
Q

how is graves eye disease managed?

A

use clinical activity score (CAS, Mouritis)
mild = topical lubricants
severe = steroids, radiotherapy, surgery

40
Q

what are the features of nodular thyroid disease?

A

asymmetrical goitre
thyroid may feel nodular
insidious onset
usually older patients

41
Q

lab tests in nodular thyroid disease?

A

increased T3/4
low TSH
antibody negative (unless co-exsisting graves disease - would show TRAb)
Scintigraphy shows high uptake

42
Q

what is a thyroid storm/crisis?

A 
medical emergency
severe hyperthyroidism
hyperthermia
resp and cardiac collapse
exaggerated reflexes
typically seen in hyperthyroid patients with an acute infection/illness or recent surgery
43
Q

mainstay of treatment in hyperthyroidism?

A

anti-thyroid drugs (ATDs)

  • carbimazole = first line
  • propylthiouracil = first line in 1st trimester of pregnancy as less potent
44
Q

specific hyperthyroidism treatment if graves disease/

A

dose titration for 12-18 months then stop medication
or
block and replace for 6 months
relapse is common

45
Q

what are some common side effects of ATDs?

A

allergy
liver disturbance
agranulocytosis (rare, happens in first 6 weeks)

46
Q

signs of agranulocytosis in ATD treatment?

A

fever
mouth ulcers
oropharyngeal infection

47
Q

what other drugs are used in hyperthyroidism?

A 
Beta blockers (propanalol, or CCB if asthmatic)
radioiodine (first line for relapsed graves, don't use in pregnancy)
48
Q

risk of radioiodine?

A

hypothyroidism when used in graves

49
Q

when might a thyroidectomy be indicated?

A

if radioiodine is contraindicated

risks = recurrent laryngeal nerve palsy, hypothyroidism

50
Q

what can cause thyroiditis?

A 
hashimotos
post partum
drug induced (amiodarone, lithium)
radiation
acute suppurative thyroiditis (bacterial)
51
Q

what are the features of subacute thyroiditis?

A 
20-50
triggered by viral infection
neck tenderness
fever
other viral symptoms
self limiting over a few months
52
Q

how does amiodarone affect the thyroid?

A

inhibits DIO1 - decreased T3 and T4, normal TSH
causes abnormal TFTs in 50% of people
causes hypothyroidism slightly more commonly than hyperthyroidism

53
Q

what is subclinical thyroid disease?

A

abnormal TSH with normal thyroid hormone

54
Q

risk factors for subclinical hypothyroidism, when is it managed?

A

if strongly TPO positive

treat if TSH >10 or pregnant

55
Q

what are the risks for subclinical hyperthyroidism and when is it treated?

A

multinodular goitre
osteoporosis
AF
treatment if TSH <0.1 or co-existing osteoporosis/AF

56
Q

what is non-thyroidal illness?

A

“sick euthyroid syndrome”

impact of incurrent illness on HPT axis causing suppression of TSH and then rise during recovery

Endocrine (45 decks)

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