Thyroid Disease Flashcards
Assessment of the Thyroid Gland:
Structural Assessment:
- normal size
- reduced/absent
- ectopic
- enlarged -> goitre
- physiological enlargement:
- adolescence
- pregnancy
- pathological enlargement
Functional Assessment:
- euthyroid
- hypothyroid
- hyperthyroid (thyrotoxic)
What is the preferred imaging modality for the thyroid gland?
ultrasound
Thyroid Gland Development:
- maturity?
- why is maternal thyroid
supply to the foetus
important in the first
trimester?
- maturity by week 11-12
- thyroxine production by week
16 - important for neurological
development
What is thyroid agenesis?
- developmental problem
- congenital hypothyroidism
- cretinism
What is aberrant thyroid?
- developmental issue
- ectopic thyroid gland
What are thyroglossal cysts?
- developmental issue
- midline neck cysts
Congenital Hypothyroidism:
- 1 in 4000 births
- universal screening in heel-
prick blood test
Thyroid Gland Developmental:
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TFTs:
- thyroid function tests
- TSH, FT4, FT3
- free thyroid hormones
Hypothyroidism: TFTs:
- TSH (high)
- Free T4 (low)
rider is forcing horse, horse isnt working
hypothalamus and pituitary producing more TRH, TSH but thyroid gland not responding and not producing T4
hence inhibitory negative feedback loop is not completed and hypothalamus/pituitary is not inhibited
Hyperthyroidism: TFTs:
- TSH (high)
- Free T4 (high)
- Free T3 (high)
Which TFT is the initial investigation of choice?
- TSH
- TSH is slow to respond to
changes in thyroid status and
takes around six weeks for
levels to equilibrate after
changes
TSH results can be misleading for:
- secondary/central
hypothyroidism - non-thyroidal illness
- recent treatment for
thyrotoxicosis
insert image above normal TFT results
Regulation of Thyroid Hormones:
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Target organ for T3 and T4?
every cell
Ultrasound of Thyroid Gland:
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What is the most common clinical problem of thyroid?
hypothyroidism
Hypothyroidism is more common in which sex?
10x more common in females
Thyroid Antibodies:
- autoimmune antibodies exist
in the population -> not
everyone will develop thyroid
disease - eg: Thyroid Peroxidase OAb
- cause of thyroid disease: TSH
receptor Ab - TPO antibodies increase risk
of hypothyroidism in the next
10 years - positive autoAb result =
confirmation - negative autoAb result does
not mean pt is clear of
autoimmune disease - can lead to both hypo and
hyperthyroidism
Hypothyroidism Symptoms:
- none
- lethargy
- weight gain
- constipation
- **cold intolerance
- facial puffiness
- dry skin
- hair loss
- hoarseness
- heavy menstrual cycle
**onwards = specific and severe
others are non-specific
Hypothyroidism Signs:
- changes in facial appearance
- puffy, pale skin
- periorbital oedema
- dry, flaking skin
- diffuse hair loss
- carpal tunnel
- effusions
- relayed reflex relaxation
- croaky voice
- goitre
**bradycardia, rare but can be in stupor or coma
** specific and severe
rest are non-specific
Features of Hypothyroidism:
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Hypothyroidism: common Clinical Presentations:
- Other Risk Factors:
- other autoimmune disorders
like T1DM, coeliac disease - family history
- immune therapy for cancer:
melanoma
- other autoimmune disorders
- Postpartum thyroiditis:
- 10% women, 8-20 weeks
postpartum - mostly self-limiting
- 10% women, 8-20 weeks
- Thyrotoxicosis:
- post-surgery
- post-radioiodine
Primary Hypothyroidism: Causes:
thyroid gland decreased function
- autoimmunity
- infection (thyroiditis)
- drug interactions
- congenital hypothyroidism
- iodine deficiency
- post hyperthyroidism
treatment
Primary Hypothyroidism: TFTs:
- TSH = high
- T4 = low
- T3 = low
due to decreased thyroid function, less T4 and hence T3 circulating, which means negative feedback loop not completed, resulting in high TSH levels
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Secondary Hypothyroidism: Causes:
disease of pituitary or
hypothalamus
- pituitary tumours
- tumours compressing
hypothalamus - sheehan syndrom (pituitary
necrosis postpartum) - TRH resistance
- TRH deficiency
- lymphocytic hyophysitis
- radiotherapy
Secondary Hypothyroidism: TFTs:
- TSH = low
- T4 = low
- T3 = low
secondary hypothyroidism is when there is a disease of the pituitary or hypothalamus
hence TRH/TSH production is limited
hence can not stimulate thyroid gland to produce T4 hence low T3
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Which type of hypothyroidism is most common?
Primary hypothyroidism is most common
Hypothyroidism: Treatment:
- core drug: levothyroxine (T4)
- daily 1.6mcg/kg
- standard treatment
- Liothyronine (T3):
- rare cases
- short half-life
Core Drug: Levothyroxine:
- half life and biological effect
- dose variations for which
categories
- monitoring
- when to take dose
- 7-10 days, much longer
biological effect - lower dose on elderly, 25-30%
higher dose during pregnancy - repeat TSH test in 4- weeks
- aim for 2mU/L
Core Drug: Levothyroxine: Side Effects:
- nausea
- vomiting
- diarrhoea
- headaches
- restlessness
- flushing/sweating
- muscle cramps
- shaking
- anxiety
- arrhythmias
Core Drug: Levothyroxine: Interactions:
- amiodarone (treats
arrhythmias) - antacids
- digoxin
Myxoedema (coma):
- severe hypothyroidism
- endocrine emergency with
high mortality
Clinical Features:
- confusion
- hypothermia
- bradycardia, hypotension,
hypoglycaemia
- peripheral oedema
Precipitants: infection, stroke, heart failure
Myxoedema (coma) Treatment:
- supportive/ICU
- Levothyroxine
- sometimes T3
- Steroids: IV hydrocostisone
Hyperthyroidism: Symptoms:
- lack of energy
- heat intolerance
- anxiety/irritability
- increased sweating
- thirst
- pruritus
- oligomenorrhoea
**weight loss associated with increased appetite, palpitations, loose bowels
**specific vs non-specific
Hyperthyroidism: Signs:
- tremor
- warm and moist skin
- tachycardia
- brisk reflexes
- eye signs
- thyroid bruit
- muscle weakness
- atrial fibrillation
Hyperthyroidism Features:
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Thyrotoxicosis: Causes:
- Grave’s Disease (autoimmune)
- thyroiditis
- toxic multinodular goitre
- toxic adenoma
- drug induced: amiodarone,
lithium
Thyrotoxicosis: Presentations:
- classic symptoms:
- investigate other illnesses
- thyroid eye disease
- post-partum
Other biochemical changes:
- Liver: transaminitis (high AST,
ALP, ALT)
- Bone: high ALP,
hypercalcaemia
- Pancytopenia/Neutropenia
(confusion etc)
Hyperthyroidism: Causes: Grave’s Disease:
- accounts for 75% of
autoimmune hyperthyroidism - autoantibody Ig that binds to
thyroid epithelial cells
mimicking the stimulatory
action of TSH - binding is to thyrotropin TSH
receptor - activity of the thyroid is
increased - Levels of T4 and T3 increase,
and the thyroid grows (goitre)
What is shown below?
Grave’s thyroiditis
gland is diffusely enlarged, fleshy and dark coloured due to increased vascularity
Hyperthyroidism: TED/TAO:
- Thyroid Eye Disease/ Thyroid
Associated Ophthalmopathy - inflammation of all orbital
tissues except eye = muscle,
eyelids, conjunctiva - itchy, dry eyes
- prominent appearance
change - diplopia
- loss of colour vision
- redness and swelling of
conjunctiva - inability to close eyes
- aching and pain behind the
eyes - proptosis
- ptosis
associated with autoimmune hyperthyroidism
What is shown below?
Thyroid Eye Disease
Hyperthyroidism: Nodules:
- toxic refers to the
overproduction of thyroid
hormones - toxic adenoma = region of
abnormal growth termed a
nodule which can be solid or
fluid filled - toxic multi-nodular goitre =
multiple nodules - both lead to generation of
excess thyroid hormones - usually benign, rarely
cancerous
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Hyperthyroidism: Causes: Thyroiditis:
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Hyperthyroidism: Grave’s Disease: Treatment:
First Line:
- radioiodine
- surgery
Risks of no treatment:
- symptoms escalate
- atrial fibrillation
- osteoporosis
Symptomatic control:
- Propranolol (beta blocker)
***if not asthmatic
Core Drug: Levothyroxine: Drug Class:
Thyroid Hormones
Hyperthyroidism: Medical Therapy:
- anti-thyroid drugs:
- carbimazole
- propylthiouracil
- course of therapy: 18-24
months - monitor reduction in T4 and
T4
Two options:
1) start with high conc
carbimazole and reduce dose
as thyroid function settles
2) continue high dose
carbimazole and then add
thyroxine
Long term medication to reduce relapse
Core Drug: Carbimazole:
- drug class
- mechanism of action
- antithyroid drugs
- inhibitors of thyroid
peroxidases: TPO or iodide
peroxidase
Core Drug: Propylthiouracil (PTU):
- drug class
- mechanism of action
- antithyroid drugs
- inhibitors of thyroid
peroxidases: TPO or iodide
peroxidase
Core Drugs: Carbimazole and Propylthiouracil: Side Effects:
- *Agranulocytosis rare but high
mortality - 1-2 months
- 2 weeks to resolve
- sore throat, mouth ulcer,
infection
Hyperthyroidism: Treatment: Radioiodine Treatment (RAI):
- medical treatment employed
first - until patient is euthyroid
- oral treatment
- I 131 concentrates in thyroid
gland - beta radiation destroys cells
(ablation)
**patient is radioactive hence
must avoid others for 2
weeks
Hyperthyroidism: Srugery:
- total or sub-total
thyroidectomy - generally with large goitres
Risks:
- anaesthetic
- neck scar (cosmetic)
- hypothyroidism
- hypoparathyroidism
- vocal cord palsy due to
recurrent laryngeal nerve
damage
Hyperthyroidism: Adenoma/Multi-toxic Goitre: Treament:
- initial medical treatment
- controls thyroid function tests
- curative treatment via
radioiodine treatment I131
Hyperthyroidism: Thyroid Eye Disease: Treatment:
- management of thyrotoxicosis
is vital - immunosupressive
- steroid/steroid-sparing agents
- radiotherapy
Surgical:
- orbital decompression
- eyelid surgery
Thyrotoxic Crisis:
- very rare complication
- usually in pts with Grave’s
Disease - high mortality
risk/acute/medical emergency - triggers: erratic compliance
with treatment, surgery,
pregnancy, acute severe
illness
Severe symptoms:
- CVS: tachycardia>140bpm,
arrhythmia, heart failure
- CNS: low GCS, agitation,
delirium
- GI: nausea, vomiting,
deranged LFTS
Thyrotoxic Crisis: Management:
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Grave’s Disease is an —– reaction to —- receptor.
- autoimmune
- TSH receptor
Thyroid nodules are detected in up to 65% of the general population.
True or False?
True
Thyroid nodules are mostly benign and insignificant findings.
True or False?
True
Goitre:
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Goitre Management:
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Thyroid Gland
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Examination of the Thyroid:
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Hypothyroidism: Investigations and Management:
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Thyrotoxicosis: Investigations and Management:
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Thyroid Nodule: Investigations and Management:
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TFTs and Causes
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