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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
How often TFTs when taking levothyroxine?
3 monthly until stabe TSH reached (2 similar measurements 3 months apart) then annually
26
adverse effects of levothyroxine
``` 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
levothyroxine drug interactions
calcium antacids iron salts take at least 4 hours apart
28
timing of levothyroxine dose
30 mins before breakfast/caffeine/other drugs
29
What primarily causes primary hyperthyroidism?
Grave's disease
30
How does Grave's disease cause hyperthyroidism?
antibodies stimuate and increase secretion of thyroid hormones
31
causes of secondary hyperthyroidism
TSH secreting pituitary tumour
32
complications of hyperthyroidism
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
features of hyperthyroidism
``` 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
management of hyperthyroidism
referral to specialist: surgery radioiodine treatment antiithyroid drugs
35
When are antithyroid drugs used in hyperthyroidism?
- 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
What can be given to treat adrenergic symptoms of hyperthyroidism?
beta blocker - titrate dose until response propranolol 10-40mg TDS/QDS MR 80-160mg OD asthma - diltiazem
37
How does radioiodine treatment work?
induces damage of DNA leading to death of thyroid cells
38
What measures should be taken after radioiodine treatment?
radioprotection - avoid close and prolonged contact with children/pregnant women for 3 weeks after
39
When is radioiodine treatment not recommended?
active thyroid eye disease (it can worsen it)
40
When is radioiodine treatment c/i?
pregnancy and breastfeeding avoid pregnancy for 6 months after men avoid having a child 4 months after
41
2 anti-thyroid drugs
carbimazole | propylthiouracil
42
How do anti-thyroid drugs work?
decrease thyroid hormone synthesis by acting as a preferred substrate for iodination by thyroid peroxidase the enzyme in thyroid hormone synthesis
43
What must be checked first before anti-thyroid hormone drugs?
FBC and LFT
44
Why is carbimazole preferred over propylthiouracil
propylthiouracil has a small risk of severe liver injury
45
When is propylthiouracil useful?
carbimazole not tolerated pregnancy/trying to conceive history of pancreatitis
46
When do Grave's disease become euthyroid with carbimazole?
after 4 - 8 weeks
47
strategy for treatment with anti-thyroid drugs
high dose carbimazole given repeat TFTs if improving use either titration block regimen or block and replace regimen
48
titration block regimen (40%)
dose adjustment every 4-6 weeks | dose reduced if T4 falls too low/levels indicate hypothyroidism
49
block and replace regime (60%)
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
adverse effects of carbimazole
``` nausea taste disturbances headache fever malaise arthralgia (joint stiffness) itch/rash bone marrow suppression - stop hepatobiliary disorders (jaundice) stop ```
51
What can be used to treat itch/rash caused by carbimazole?
antihistamines
52
dose of carbimazole
15 - 40mg daily reduced to maintenance dose of 5 - 15mg usually for 12 - 18 months block and replace: 40 - 60mg daily
53
examples of bone marrow suppression caused by carbimazole
neutropenia and agranulocytosis
54
What are signs of bone marrow suppression caused by carbimazole?
signs of infection, sore throat and fever
55
What is preformed if there are signs of bone marrow suppression/infection and when? (carbimazole)
white blood cell count | on the same day
56
adverse effects of propylthiouracil
``` leucopenia cutaneous vasculitis aplastic anaemia nephritis hepatic disorders - hepatitis, hepatic failure, hepatic necrosis ```
57
propylthiouracil dose
200 - 400mg daily in divided doses maintained until patient is euthyroid dose gradually reduced to maintenance of 50 - 150mg daily in divided doses
58
Which is the more active thyroid hormone?
T3 | T4 converted to T3 in peripheral tissues

PHA223 (43 decks)

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