hypothyroidism Flashcards
signs and symptoms of hypothyroidism
- fatigue
- weight gain
- constipation
- menstrual irregularities
- depression
- dry skin
- intolerance to cold
- reduced body and scalp hair
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
diarrhoea is a symptom of HYPERthyroidism, constipation is a sign of HYPO
complications of hypothyroidism
- 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
what is myxoedema coma
- 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
if current or non thyroidal illness is suspected, should you check TFTs
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
what is primary hypothyroidism and what are the classifications
- condition arises from thyroid gland itself rather than pituitary or hypothalamic disorder
- can be overt or subclinical
primary hypothyroidism is more common in…
females
primary hypothyroidism may be caused by
- iodine deficiency
- autoimmune disease e.g. Hashmitos thyroiditis
- radiotherapy
- post ablative therapy or surgery
- drugs e.g. amiodarone, lithium
- transient thyroidiitis
- thyroid infiltrative disorders
what is overt hypothyroidism
TSH above reference
FT4 below reference
what is overt hypothyroidism in pregnancy
based on high TSH using trimester specific reference ranges regardless of FT4 levels
subclinical hypothyroidism
TSH above reference
FT4 and FT3 within reference
what is secondary hypothyroidism
- rare
- caused by pituitary or hypothalamic disorder
- e.g. underactive pituitary gland causes underachieve thyroid
what are the results in secondary hypothyroidism
TSH low, normal, or rarely raised
FT4 is low
a patient presents with loss of lateral eyebrows, coarse dry hair and skin, oedema, fatigue and weight gain. what does this suggest
hypothyroidism
when does the hypothyroid phase of postpartum thyroiditis usually occur and how long does it typically last
hypothyroid phase of PPT usually occurs between 3-8 months (most often at 6 months) postpartum and typically lasts 4-6 months
bloods to take when suspecting hypothyroidism and repeat testing
- 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
when to suspect secondary hypothyroidism
if clinical features are suggestive and TSH levels are inappropriately low (may be normal), and FT4 is also low
consider checking additional bloods if primary hypothyroidism is suspected:
- 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
how can obesity affect TFTs
obesity can affect HPT axis and serum TSH can become raised in overweight or obese people, which may falsely suggest subclinical hypothyroidism
how can biotin affect hormone assays
biotin can lead to….
- False Low TSH Levels: This may suggest hyperthyroidism
- Altered T3 and T4 Levels: can cause falsely elevated or decreased free T4 and T3 levels, complicating the diagnosis of hyperthyroidism or hypothyroidism.
can a pt with hypothyroidism have a goitre
yes
screening for hypothyroidism in pt taking lithium and amiodarone
screen at baseline and every 6 months
if amiodarone stopped, continue monitoring for a further 12 months
screening for hypothyroidism in pt who have has radio iodine therapy or surgery for hyperhtyroidism
screen 4-8 weeks post treatment, then every 3 months for a year, then yearly
1st line treatment for overt hypothyroidism & aim of treatment & what to do if symptoms persist
- 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
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
up to 6 months of treatment with levothyroxine
how often should you consider monitoring TSH levels after initiation of levothyroxine treatment
every 3 months after initiation until stable level, then yearly
which patients should you consider also monitoring FT4 in (in additional to TSH in pt taking levothyroxine for overt hypothyroidism)
consider also monitoring ft4 in pt who continue to be symptomatic
is the use of natural thyroid extract recommended and why
not recommended due to uncertainty around the long term adverse effects and insufficient evidence of benefit over levothyroxine
discuss use of liothyronine monotherapy or combination with levothyroxine for pt with overt hypothyroidism
not recommend due to uncertainty around the long term adverse effects and insufficient evidence of benefit over levothyroxine
how often to check TSH levels once pt is stable on levothyroxine for overt hypothyroidism
annually
what does it mean when a pt is stable on levothyroxine for overt hypothyroidism
Stable = 2 similar measurements within the reference range 3 months apart
what to do if TFTs remain abnormal or there are persistent symptoms despite adequate or escalating LT4 doses
Check for underlying causes and consider referral to endocrinology if no cause found
if pt has suspected adverse effects or feels more unwell after starting LT4 therapy
- 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
what effect can weight gain and pregnancy have on LT4 requirements
they may increase LT4 requirements i.e. dose increase needed
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.
○ 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
when should levothyroxine be considered for pt with subclinical hypothyroidism
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
how often to review pt on levothyroxine treatment for subclinical hypothyroidism
○ 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
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
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
how often should you consider measuring TSH and FT4 in pt with untreated subclinical hypothyroidism or if LT4 therapy has been stopped
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
management of secondary hypothyroidism
If suspected, refer ungently to endocrinologist to assess underlying cause
what to do with females with hypothyroidism who are planning pregnancy or are pregnant
refer to endocrinologist
what to advice females who are planning pregnancy and TFTs are not in range
advise delaying conception until stabilised on levo LT4
what to do if pregnancy is confirmed in females with hypothyroidism
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
will dose of levothyroxine need adjustment in pregnancy and why
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
what to do if female has pregnancy suspected or confirmed
seek immediate medical advice
referral to endocrinology specialist for women with overt or subclinical hypothyroidism who is
- 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
levothyroxine contraindicated in
Thyrotoxicosis
MHRA advice for patients who experience symptoms on switching between different levothyroxine products
- 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
food interactions with levothyroxine
food, including dietary fibre, milk, soya products and coffee may decrease absorption of levo
does levothyroxine have any warning labels
no
counselling on when to take levothyroxine dose
dose to be taken preferably 30–60 minutes before breakfast, caffeine-containing liquids (e.g. coffee, tea), or other medication.
cautions for levothyroxine
- 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)
why is baseline ECG valuable in pt with cv disorders who are on levo
changes induced by hypothyroidism can be confused with ishcaemia
adverse effects of levothyroxine usually occur with
excessive dosage and usually stop on reduction of dosage or withdrawal of treatment for a few days
adverse effects of levothyroxine may include
- 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
what to do if initial dosage in pt with CV disorders have side effects
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
levothyroxine requirement may …… in pregnancy
increase
levothyroxine monitoring in pregnancy
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
monitoring of pt parameters when used for primary hypothyroidism
- 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
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
antacids can reduce absorption of levothyroxine, so separate doses by at least 4 hours
a patient who has T2D has been started on levothyroxine. what might this mean for the anti diabetic drugs?
treatment with levothyroxine may increase blood glucose levels
therefore anti diabetic doses including insulin may need to be increased
a patient who takes anti epileptic drugs (e.g. 3P1C) has been diagnosed with primary hypothyroidism what might this mean for levothyroxine
AEDs can accelerate levo metabolism and thus increase LT4 requirements
they increase the risk of hypothyroidism
pt may require higher doses of LT4
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
advice pt to leave 4 hour gap as iron reduced absorption of levothyroxine
calcium and levothyroxine
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
amiodarone and levo
Amiodarone is predicted to increase the risk of thyroid dysfunction when given with Levothyroxine. It can cause either hypo or hyperthyroidism due to its high iodine content. This alters effectiveness of levothyroxine. Manufacturer advises avoid.
Regular thyroid function tests are crucial for managing and adjusting doses appropriately.
Hypothyroidism can be treated with replacement therapy without withdrawing amiodarone if it is essential; careful supervision is required.
levothyroxine and digoxin
Levothyroxine is predicted to affect the concentration of Digoxin. Manufacturer advises monitor and adjust dose.
HRT and levothyroxine
oral Hormone replacement therapy is predicted to decrease the effects of Levothyroxine. Manufacturer makes no recommendation. may require increased dose of lt4
liothyronine and levothyroxine equivalent doses
20–25 micrograms of liothyronine sodium is equivalent to approximately 100 micrograms of levothyroxine sodium.
liothyronine - switching to different brands
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.
how does hypothyroidism happen
results from underproduction and secretion of thyroid hormones
Why is T3 often not included for diagnosis of hypothyroidism
T3 is not used for diagnosis because it is often normal in hypothyroidism and not a reliable indicator.
what is the correlation between CV disorders and hypothyroidism
Hypothyroidism can lead to bradycardia, increased cholesterol, and increased risk of heart disease.
in eldelry or cardiac patients, what should you do
lower dose and slower titration
Start levothyroxine low and slow in elderly/cardiac patients to avoid straining the heart. Rapid increases in metabolism can lead to arrhythmias, angina, or heart failure.
Why should a patient be advised to report symptoms such as chest pain or palpitations when starting or adjusting levothyroxine?
Levothyroxine can increase metabolism, potentially triggering heart issues, so report symptoms like palpitations promptly.
Increased Metabolism: When we say increased metabolism in the context of thyroid hormone, we mean that thyroid hormones (T3 and T4) stimulate nearly all tissues in the body to work harder and faster.
For cardiac patients (especially elderly or those with underlying conditions like ischemic heart disease), the heart may not be able to keep up with the increased demand, potentially triggering arrhythmias, angina, or even heart failure.
What considerations should be taken when prescribing levothyroxine to a patient with adrenal insufficiency?
For patients with adrenal insufficiency, treat with corticosteroids before starting levothyroxine to avoid adrenal crisis.
Corticosteroid therapy protects against adrenal crisis by preparing the adrenal system before levothyroxine raises metabolic activity.
