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hypothyroidism Flashcards

1
Q

how does hypothyroidism happen

A

results from underproduction and secretion of thyroid hormones

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1
Q

signs and symptoms of hypothyroidism

A
  • fatigue
  • weight gain
  • constipation
  • menstrual irregularities
  • depression
  • dry skin
  • intolerance to cold
  • reduced body and scalp hair
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2
Q

which one of the following is not a sign of hypothyroidism
- weight gain
- fatigue
- diarrhoea
- reduced body and scalp hair
- dry skin
- depression
- menstrual irregularities

A

diarrhoea is a symptom of HYPERthyroidism, constipation is a sign of HYPO

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3
Q

complications of hypothyroidism

A
  • dyslipidaemia
  • CHD
  • stroke
  • neurological and cognitive impairments
  • HF
  • metabolic syndrome
  • impaired fertility
  • pregnancy complications - adverse maternal and foetal outcomes
  • impaired conc and/or memory
  • rare: myxoedema coma
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4
Q

what is myxoedema coma

A
  • rare but life threatening medical emergency
  • rare complication of hypothyroidism
  • severe hypothyroidism with phsyiological decompensation
  • usually occurs in pt with long standing, undiagnosed hypothyroidism
  • often precipitated by infected, cerebrovascular disease, HF, trauma, drug therapy etc
  • generally pt is severely ill with significant hypothermia and depressed mental status
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5
Q

if current or non thyroidal illness is suspected, should you check TFTs

A

do not check TFTs during acute illness unless it is felt that symptoms may be due to thyroid dysfunction as acute non-thryodial illness is likely to affect TFTs

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6
Q

what is primary hypothyroidism and what are the classifications

A
  • condition arises from thyroid gland itself rather than pituitary or hypothalamic disorder
  • can be overt or subclinical
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7
Q

primary hypothyroidism is more common in…

A

females

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8
Q

primary hypothyroidism may be caused by

A
  • iodine deficiency
  • autoimmune disease e.g. Hashmitos thyroiditis
  • radiotherapy
  • post ablative therapy or surgery
  • drugs e.g. amiodarone, lithium
  • transient thyroidiitis
  • thyroid infiltrative disorders
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9
Q

what is overt hypothyroidism

A

TSH above reference
FT4 below reference

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10
Q

what is overt hypothyroidism in pregnancy

A

based on high TSH using trimester specific reference ranges regardless of FT4 levels

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11
Q

subclinical hypothyroidism

A

TSH above reference
FT4 and FT3 within reference

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12
Q

what is secondary hypothyroidism

A
  • rare
  • caused by pituitary or hypothalamic disorder
  • e.g. underactive pituitary gland causes underachieve thyroid
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13
Q

what are the results in secondary hypothyroidism

A

TSH low, normal, or rarely raised
FT4 is low

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14
Q

a patient presents with loss of lateral eyebrows, coarse dry hair and skin, oedema, fatigue and weight gain. what does this suggest

A

hypothyroidism

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15
Q

when does the hypothyroid phase of postpartum thyroiditis usually occur and how long does it typically last

A

hypothyroid phase of PPT usually occurs between 3-8 months (most often at 6 months) postpartum and typically lasts 4-6 months

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16
Q

bloods to take when suspecting hypothyroidism and repeat testing

A
  • check TSH, if high then measure FT4 within same sample
  • in non-pregnancy, repeat 3-6 months after initial result to exclude other causes of transiently raised TSH and to confirm diagnosis
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17
Q

when to suspect secondary hypothyroidism

A

if clinical features are suggestive and TSH levels are inappropriately low (may be normal), and FT4 is also low

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18
Q

consider checking additional bloods if primary hypothyroidism is suspected:

A
  • FBC and B12 to assess for possible associated pernicious anaemia
  • HbA1c to assess for associated T1DM
  • coeliac serology to assess for coeliac disease if a diagnosis of autoimmune thyroid disease is suspected
  • serum lipids to assess for associated dyslipidaemia
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19
Q

how can obesity affect TFTs

A

obesity can affect HPT axis and serum TSH can become raised in overweight or obese people, which may falsely suggest subclinical hypothyroidism

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20
Q

how can biotin affect hormone assays

A

can cause increased TSH and normal to increased FT4

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21
Q

can a pt with hypothyroidism have a goitre

A

yes

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22
Q

screening for hypothyroidism in pt taking lithium and amiodarone

A

screen at baseline and every 6 months
if amiodarone stopped, continue monitoring for a further 12 months

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23
Q

screening for hypothyroidism in pt who have has radio iodine therapy or surgery for hyperhtyroidism

A

screen 4-8 weeks post treatment, then every 3 months for a year, then yearly

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24
Q

1st line treatment for overt hypothyroidism & aim of treatment & what to do if symptoms persist

A
  • levothyroxine (LT4) monotherapy
  • aim to maintain TSH within reference
  • if symptoms persist, even after achieving normal TSH levels, consider adjusting the dose to achieve optimal well-being whilst avoiding doses that cause TSH suppression or thyrotoxicosis
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25
Q

for patients whose TSH levels were very high before starting treatment or who have had prolonged period of untreated disease, how long can TSH take to return to reference

A

up to 6 months of treatment with levothyroxine

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26
Q

how often should you consider monitoring TSH levels after initiation of levothyroxine treatment

A

every 3 months after initiation until stable level, then yearly

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27
Q

which patients should you consider also monitoring FT4 in (in additional to TSH in pt taking levothyroxine for overt hypothyroidism)

A

consider also monitoring ft4 in pt who continue to be symptomatic

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28
Q

is the use of natural thyroid extract recommended and why

A

not recommended due to uncertainty around the long term adverse effects and insufficient evidence of benefit over levothyroxine

29
Q

discuss use of liothyronine monotherapy or combination with levothyroxine for pt with overt hypothyroidism

A

not recommend due to uncertainty around the long term adverse effects and insufficient evidence of benefit over levothyroxine

30
Q

how often to check TSH levels once pt is stable on levothyroxine for overt hypothyroidism

A

annually

31
Q

what does it mean when a pt is stable on levothyroxine for overt hypothyroidism

A

Stable = 2 similar measurements within the reference range 3 months apart

32
Q

what to do if TFTs remain abnormal or there are persistent symptoms despite adequate or escalating LT4 doses

A

Check for underlying causes and consider referral to endocrinology if no cause found

33
Q

if pt has suspected adverse effects or feels more unwell after starting LT4 therapy

A
  • Consider possible under or over treatment with LT4
  • Consider whether associated endocrine disease e.g. Addison’s is a possibility, and arrange specialist endocrinology referral depending on clinical judgement
34
Q

what effect can weight gain and pregnancy have on LT4 requirements

A

they may increase LT4 requirements i.e. dose increase needed

35
Q

if TFTs remain abnormal or pt has persistent symptoms despite adequate or escalating LT4 doses, assess for any possible causes and manage appropriately e.g.

A

○ Non-compliance
○ Drug interactions, including multivitamins and OTC meds
○ GI conditions causing malabsorption e.g. coeliac, H. pylori gastritis, atrophic gastritis/pernicious anaemia, giardiasis, IBD - may reduce absorption of LT4 in gut
○ Simultaneous intake with food and rink e.g. milk, coffee, grapefruit juice, soya, papaya etc -impairs absorption of LT4
Weight gain and pregnancy which may increase LT4 requirements

36
Q

when should levothyroxine be considered for pt with subclinical hypothyroidism

A

For pt who have a TSH level of 10 mIU/L or higher and FT4 level within reference on 2 separate occasions 3 months apart

37
Q

how often to review pt on levothyroxine treatment for subclinical hypothyroidism

A

○ Consider checking FT4 in addition if pt has ongoing symptoms on treatment
○ If symptoms persist, consider adjusting dose of LT4 further to achieve optimal well being, taking care to avoid over treatment
○ Once TSH stable (2 similar measurements within ref range 3 months apart), check TSH annually

38
Q

what to do in pt who have subclinical hypothyroidism and are symptomatic, under 65, with TSH above reference but lower than 10mlU/L on 2 separate occasions 3 months apart

A

consider 6 month trial levothyroxine
if symptoms do not improve after initiation, remeasure TSH
if levels remain elevated, adults dose
if symptoms persist when serum TSH within reference, consider stopping and assessing for alternative causes

39
Q

how often should you consider measuring TSH and FT4 in pt with untreated subclinical hypothyroidism or if LT4 therapy has been stopped

A

Annually if clinical feature suggesting underlying thyroid disease e.g. previous thyroid surgery or raised levels of TPOAbs, or
Once every 2-3 years if no features suggesting underlying thyroid disease

40
Q

management of secondary hypothyroidism

A

If suspected, refer ungently to endocrinologist to assess underlying cause

41
Q

what to do with females with hypothyroidism who are planning pregnancy or are pregnant

A

refer to endocrinologist

42
Q

what to advice females who are planning pregnancy and TFTs are not in range

A

advise delaying conception until stabilised on levo LT4

43
Q

what to do if pregnancy is confirmed in females with hypothyroidism

A

urgently measure TFTs and discuss initiation or changes to levothyroxine treatment and TFT monitoring with endocrinologist whilst awaiting review, to reduce risk of obstetric and neonatal complications

44
Q

will dose of levothyroxine need adjustment in pregnancy and why

A

There will likely be increased demand for LT4 treatment during pregnancy and LT4 dose needs to be adjusted as early as possible in pregnancy to reduce chance of obstretic and neonatal complications

45
Q

what to do if female has pregnancy suspected or confirmed

A

seek immediate medical advice

46
Q

referral to endocrinology specialist for women with overt or subclinical hypothyroidism who is

A
  • Planning pregnancy
  • Pregnant (urgent TFTs needed and LT4 dose should be adjusted on specialist advice)
  • Postpartum and was treated with LT4 in pregnancy
  • Diagnosed with postpartum thyroiditis
47
Q

levothyroxine contraindicated in

A

Thyrotoxicosis

48
Q

MHRA advice for patients who experience symptoms on switching between different levothyroxine products

A
  • Small number of people treated with levothyroxine report symptoms they are often consistent with thyroid dysfunction when their tablets are changed to a different product
    ○ If a patient reports symptoms after changing their levothyroxine product, consider testing thyroid function
    ○ If persistent symptoms are reported when switching between different levothyroxine tablet formulations, consider consistently prescribing a specific product known to be well tolerated by the person
    ○ If symptoms or poor control of thyroid function persist despite adhering to a specific product, consists prescribing levothyroxine in an oral solution formulation
    ○ Report suspected adverse reactions to levothyroxine medicines, including symptoms after switching products to the yellow card scheme
49
Q

food interactions with levothyroxine

A

food, including dietary fibre, milk, soya products and coffee may decrease absorption of levo

50
Q

does levothyroxine have any warning labels

A

no

51
Q

counselling on when to take levothyroxine dose

A

dose to be taken preferably 30–60 minutes before breakfast, caffeine-containing liquids (e.g. coffee, tea), or other medication.

52
Q

cautions for levothyroxine

A
  • cv disorders
  • diabetes inspidis
  • DM (dose of anti diabetic drugs incl insulin may need to be increased)
  • elderly
  • hypertension
  • long standing hypothyroidism
  • MI
  • myocardial insufficiency
  • panhypopituitarism and predisposition to adrenal insufficiency (stat CC therapy before starting levo)
53
Q

why is baseline ECG valuable in pt with cv disorders who are on levo

A

changes induced by hypothyroidism can be confused with ishcaemia

54
Q

adverse effects of levothyroxine usually occur with

A

excessive dosage and usually stop on reduction of dosage or withdrawal of treatment for a few days

55
Q

adverse effects of levothyroxine may include

A
  • GI e.g. diarrhoea, vomiting
  • CV e.g. angina, arrhythmias, palpitations, tachycardia
  • immunological e.g. hypersensitivity including rash, itch, oedema etc
  • metabolic e.g. weight oss
  • MSK e.g. arthralgia and muscle weakness
  • neurological e.g. anxiety, tremor, insomnia
  • psychiatric e.g. mania
  • reproductive e.g. menstrual irregulatirites
  • general e.g. headache, flushing, sweating, fever, heat intolerance
56
Q

what to do if initial dosage in pt with CV disorders have side effects

A

if metabolism increases too rapidly (causing diarrhoea, nervoussnes, rapid pulse, insomnia, tremors, and sometimes anginal pain where there is latent MI) reduce dose or withhold for 1-2 days and start again at lower dose

57
Q

levothyroxine requirement may …… in pregnancy

A

increase

58
Q

levothyroxine monitoring in pregnancy

A

assess maternal thyroid function before conception if possible, at diagnosis of pregnancy, at antenatal booking, during 2nd and 3rd trimesters, and after delivery
more frequent monitoring is required on initiation or adjustment

59
Q

monitoring of pt parameters when used for primary hypothyroidism

A
  • consider monitoring TSH every 3 months until stable (two similar measurements within ref range, 3 months apart), then yearly
  • consider measuring FT4 if symptoms of hypothyroidism persist after starting levo
60
Q

a patient comes in to buy an antacid (e.g. calcium carbonate, or aluminium and magnesium containing). You check her PMR and see she takes levothyroxine. what do you do

A

antacids can reduce absorption of levothyroxine, so separate doses by at least 4 hours

61
Q

a patient who has T2D has been started on levothyroxine. what might this mean for the anti diabetic drugs?

A

treatment with levothyroxine may increase blood glucose levels
therefore anti diabetic doses including insulin may need to be increased

62
Q

a patient who takes anti epileptic drugs (e.g. 3P1C) has been diagnosed with primary hypothyroidism what might this mean for levothyroxine

A

AEDs can accelerate levo metabolism and thus increase LT4 requirements
they increase the risk of hypothyroidism
pt may require higher doses of LT4

63
Q

a patient who regularly takes levothyroxine has just bought in a prescription for ferrous sulphate 200mg tabs, one to be taken daily. what should you do

A

advice pt to leave 2 hour gap as ferrous sulphate reduced absorption of levothyroxine

64
Q

calcium and levothyroxine

A

oral calcium (e.g. phosphate, carbonate, acetate etc) predicted to decrease the absorption of oral Levothyroxine. Manufacturer advises separate administration by at least 4 hours

65
Q

amiodarone and levo

A

Amiodarone is predicted to increase the risk of thyroid dysfunction when given with Levothyroxine. Manufacturer advises avoid.

66
Q

levothyroxine and digoxin

A

Levothyroxine is predicted to affect the concentration of Digoxin. Manufacturer advises monitor and adjust dose.

67
Q

HRT and levothyroxine

A

oral Hormone replacement therapy is predicted to decrease the effects of Levothyroxine. Manufacturer makes no recommendation. may require increased dose of lt4

68
Q

liothyronine and levothyroxine equivalent doses

A

20–25 micrograms of liothyronine sodium is equivalent to approximately 100 micrograms of levothyroxine sodium.

69
Q

liothyronine - switching to different brands

A

Patients switched to a different brand should be monitored (particularly if pregnant or if heart disease present) as brands without a UK licence may not be bioequivalent. Pregnant women or those with heart disease should undergo an early review of thyroid status, and other patients should have thyroid function assessed if experiencing a significant change in symptoms. If liothyronine is continued long-term, thyroid function tests should be repeated 1–2 months after any change in brand.

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