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PHA223 > Thyroid disorders in practice > Flashcards

Thyroid disorders in practice Flashcards

1
Q

What hormones does the thyroid gland produce?

A

T3 - tri-iodothyronine

T4 - thyroxine

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2
Q

2 drugs that can induce thyroid disorders

A

amiodarone

lithium

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3
Q

How does amiodarone cause hypothyroidism?

A

blocks the conversion of T4 to T3

causes an increase in TSH

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4
Q

How does amiodarone cause hyperthyroidism?

A

due to the iodine content of the drug

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5
Q

TFT monitoring before starting amiodarone

A

TSH
T3
T4
thyroid antibodies

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6
Q

TFT during treatment of amiodarone

A

TSH
T3
T4

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7
Q

Why do you do TFT after stopping amiodarone?

A

due to its long half life

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8
Q

Hypothyroidism occurs while taking amiodarone

A

add levothyroxine and continue amiodarone

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9
Q

How does lithium cause hypothyroidism?

A

inhibits iodine uptake and thyroid hormone release

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10
Q

TFT results for hypothyroidism?

A

high TSH

low T4

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11
Q

TFT results for hyperthyroidism

A

low TSH

high T4

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12
Q

TFT results for subclinical hypothyroidism

A

high TSH

normal T4

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13
Q

TFT results for subclinical hyperthyroidism

A

low TSH

normal T4

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14
Q

What is hypothyroidism?

A

impaired production of thyroid hormones

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15
Q

What is primary hypothyroidism?

A

failure of the thyroid gland to produce thyroid hormones

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16
Q

What is secondary hypothyroidism?

A

underproduction of TSH by the pituitary gland

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17
Q

subclinical hypothyroidism

A

usually asymptomatic
don’t need treatment unless symptoms (levothyroxine trial)
screening of TFTs

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18
Q

features of hypothyroidism

A 
fatigue
cold intolerance
weight gain
constipation
myalgia (muscle pain)
menstrual irregularities
depression
impaired concentration/memory
dry skin/hair
hair loss
thyroid pain
oedema
vocal changes (hoarness)
goitre
bradycardia
diastolic hypertension
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19
Q

complications of hypothyroidism

A

CV - dyslipidaemia, CHD, HF
reproductive - fertility, pregancy complications
neurological - deafness, concentration, memory
myxoedema coma - emergency

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20
Q

When to refer to endocrinologist with hypothyroidism?

A 
goitre
suspected Addison's disease
pregnant/planning pregnancy
cardiac disease
atypical thryoid tests
drug causes
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21
Q

1st line treaement for hypothyroidism

A

levothyroxine

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22
Q

dose of levothyroxine (under 65)

A

1.6 mcg/kg/day (nearest 25mcg)

increase 25-50 mcg every 3-4 weeks

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23
Q

maintenance dose of levothyroxine

A

100 - 200 mcg daily

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24
Q

levothyroxine dose over 60-65 years or IHD

A

25-50 mcg adjusted by 25mcg

25
Q

How often TFTs when taking levothyroxine?

A

3 monthly until stabe TSH reached (2 similar measurements 3 months apart)
then annually

26
Q

adverse effects of levothyroxine

A 
GI disturbances
CV - arrhythmais, tachycardia
flushing, fever, heat intolerance
weight loss
hypersensitivity rxns - rash, oedema
muscle cramps, weakness
anxiety, tremour, restlessness, insomnia
mania
menstrual irregularities
headache
27
Q

levothyroxine drug interactions

A

calcium
antacids
iron salts
take at least 4 hours apart

28
Q

timing of levothyroxine dose

A

30 mins before breakfast/caffeine/other drugs

29
Q

What primarily causes primary hyperthyroidism?

A

Grave’s disease

30
Q

How does Grave’s disease cause hyperthyroidism?

A

antibodies stimuate and increase secretion of thyroid hormones

31
Q

causes of secondary hyperthyroidism

A

TSH secreting pituitary tumour

32
Q

complications of hyperthyroidism

A

CV - AF, increased stroke risk
osteoporosis
eye disease - vision loss
thyroid storm - release of large amts of thyroid hormone, sudden worsening of symptoms, emergency, loss of consciousness

33
Q

features of hyperthyroidism

A 
breathlessness
hyperactivity
insomnia, irritability
palpitations
exercise intolerance
heat intolerance
fatigue
muscle weakness
incresed appetite, weight loss
diarrhoea
infertility, oligomenorrhoea, amenorrhoea
polyuria
itch
reduced libido, gynaecomastia (men)
hyperglycaemia (DM)
sinus tachycardia, AF, HF
eye signs
goitre
muscle wasting
34
Q

management of hyperthyroidism

A

referral to specialist:
surgery
radioiodine treatment
antiithyroid drugs

35
Q

When are antithyroid drugs used in hyperthyroidism?

A
  • ST when waiting for specialist review
  • ST prep for radioiodine treatment/surgery
  • medium term when inducing remission of Grave’s
  • LT radioiodine/surgery c/i/declines
36
Q

What can be given to treat adrenergic symptoms of hyperthyroidism?

A

beta blocker - titrate dose until response
propranolol 10-40mg TDS/QDS
MR 80-160mg OD
asthma - diltiazem

37
Q

How does radioiodine treatment work?

A

induces damage of DNA leading to death of thyroid cells

38
Q

What measures should be taken after radioiodine treatment?

A

radioprotection - avoid close and prolonged contact with children/pregnant women for 3 weeks after

39
Q

When is radioiodine treatment not recommended?

A

active thyroid eye disease (it can worsen it)

40
Q

When is radioiodine treatment c/i?

A

pregnancy and breastfeeding

avoid pregnancy for 6 months after
men avoid having a child 4 months after

41
Q

2 anti-thyroid drugs

A

carbimazole

propylthiouracil

42
Q

How do anti-thyroid drugs work?

A

decrease thyroid hormone synthesis by acting as a preferred substrate for iodination by thyroid peroxidase the enzyme in thyroid hormone synthesis

43
Q

What must be checked first before anti-thyroid hormone drugs?

A

FBC and LFT

44
Q

Why is carbimazole preferred over propylthiouracil

A

propylthiouracil has a small risk of severe liver injury

45
Q

When is propylthiouracil useful?

A

carbimazole not tolerated
pregnancy/trying to conceive
history of pancreatitis

46
Q

When do Grave’s disease become euthyroid with carbimazole?

A

after 4 - 8 weeks

47
Q

strategy for treatment with anti-thyroid drugs

A

high dose carbimazole given
repeat TFTs
if improving use either titration block regimen or block and replace regimen

48
Q

titration block regimen (40%)

A

dose adjustment every 4-6 weeks

dose reduced if T4 falls too low/levels indicate hypothyroidism

49
Q

block and replace regime (60%)

A

anti-thyroid drug used to block syhtnesis of thyroid hormone
T4 is monitored
levothyroxine is added
adjustments to levothyroxine dose made to maintain T4 levels in the reference range

50
Q

adverse effects of carbimazole

A 
nausea
taste disturbances
headache
fever
malaise
arthralgia (joint stiffness)
itch/rash
bone marrow suppression - stop
hepatobiliary disorders (jaundice) stop
51
Q

What can be used to treat itch/rash caused by carbimazole?

A

antihistamines

52
Q

dose of carbimazole

A

15 - 40mg daily
reduced to maintenance dose of 5 - 15mg
usually for 12 - 18 months
block and replace: 40 - 60mg daily

53
Q

examples of bone marrow suppression caused by carbimazole

A

neutropenia and agranulocytosis

54
Q

What are signs of bone marrow suppression caused by carbimazole?

A

signs of infection, sore throat and fever

55
Q

What is preformed if there are signs of bone marrow suppression/infection and when? (carbimazole)

A

white blood cell count

on the same day

56
Q

adverse effects of propylthiouracil

A 
leucopenia
cutaneous vasculitis
aplastic anaemia
nephritis
hepatic disorders - hepatitis, hepatic failure, hepatic necrosis
57
Q

propylthiouracil dose

A

200 - 400mg daily in divided doses
maintained until patient is euthyroid
dose gradually reduced to maintenance of 50 - 150mg daily in divided doses

58
Q

Which is the more active thyroid hormone?

A

T3

T4 converted to T3 in peripheral tissues

PHA223 (43 decks)

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