Disorders of thyroid gland Flashcards
Describe the different types of hypothyroidism
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Primary hypothyroidism (95%): inadequate production by gland
- Overt (OH): TSH elevated; Free T4 reduced
- Subclinical (SCH): TSH elevated; T3 and T4 normal
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Secondary hypothyrodism: insufficient thyroid stimulation
- TSH low/normal; Free T4 reduced
Name five causes of primary hypothyroidism
- Iodine deficiency: commonest worldwide
- Autoimmune: commonest in UK
- Hashimoto’s thyroiditis: goitre present
- Atrophic thyroiditis: goitre absent due to later stage
- Iatrogenic: Radioactive iodine; neck irradiation; post-neck surgery
- Carbimazole; propythiouracil; lithium; amiodarone; valproate
- Congenital agenesis; absent enzymes
- Subacute (de Quervain’s) thyroiditis; postpartum thyroiditis
- Tumour; sarcoidosis; TB
Give three causes of secondary hypothyroidism
Pituitary or hypothalamic dysfunction:
- Tumours: eg. pituitary adenoma; glioma
- Surgery; radiotherapy; trauma
- Pituitary infarction
- Sheenhan’s syndrome: postpartum pituitary necrosis
- Amyloidosis; sarcoidosis; haemachromatosis; TB
- Idiopathic hypothalamic disease
- Cocaine; dopamine; steroids; metformin
Define Hashimoto’s thyroiditis
An autoimmune hypothyroidism due to the presence of thyroid peroxidase (TPO) antibodies
Thyroid peroxidase antibodies prevent the oxidation of iodide to iodine
Iodine is required to produce thyroid hormones
Differentiated from atrophic thyroiditis by presence of goitre
What pregnancy complications can occur with hypothyroidism?
- Eclampsia
- Anaemia
- Prematurity
- Low birthweight
- Stillbirth
- Postpartum haemorrhage
List five symptoms of hypothyroidism
- Tiredness/malaise
- Weight gain; loss of appetite
- Cold intolerance
- Goitre; thyroid pain
- Dry skin and hair loss (especially lateral eyebrows)
- Poor memory, depression, poor libido, psychosis
- Arthralgia, myalgia, weakness
- Constipation
- Menorrhagia or oligomenorrhoea; infertility
- Coma
List three signs of hypothyroidism
- Bradycardia
- Dry skin and hair
- Mental slowness
- Delayed reflexes (Woltman’s sign of hypothyroidism)
- Deep voice due to goitre compressing RLN
- Periorbital oedema
- Cold peripheries, carpal tunnel syndrome
How is overt hypothyroidism treated?
- Levothyroxine replacement therapy for life: titrate to TSH
- Under 65 without CV disease: Start at 1.6 mcg/kg/d
- 65+ or CV disease: Start at 25-50 mcg/d
- Consider TSH monitoring every 3/12 till stable, then annually
How is subclinical hypothyroidism treated?
- Consider levothyroxine if:
- TSH 10+ mIU/L on two occasions 3/12 apart
- Or <10 mIU/L on two occassions 3/12 apart + symptoms
What are myxoedema coma and myxoedema madness?
-
Myxoedema coma: rare, life-threatening medical emergency
- Untreated severe hypothyroidism
- Lethargy; bradycardia; hypotherami; seizures; coma
- Myxoedema madness
- Dementia/psychosis in severe hypothyroidism of the elderly
Request three investigations for suspected thyroid disorders
- TFTs: TSH; Free T4
- Other autoimmune conditions
- FBC: pernicious anaemia
- HbA1c: T1DM
- tTG; Total IgA: Coeliac disease
- Serum lipids
- TPO antibodies
- TSH receptor antibodies
- USS thyroid
Describe the different types of hyperthyroidism
- Primary hyperthyroidism:
- Overt: TSH reduced; Free T4 and/or T3 raised
- Subclinical: TSH reduced: Free T4 and T3 normal
Thyrotoxicosis without hyperthyroidism: Typically transient
Provide three risk factors for hyperthyroidism
- Female (10:1)
- FHx of thyroid disease
- Smoking: dose-dependent for Grave’s disease
- Low iodine intake wiht subsequent increase
- Co-existant autoimmune conditions
Name three causes of hyperthyroidism
- Grave’s disease (80%)
- Toxic multinodular goitre: older adults
- Toxic thyroid nodule/adenoma (5%)
- TSH-secreteing pituitary adenoma
- High hCG eg. gestational thyrotoxicosis; hyperemesis gravidarum
- de Quervain’s thyroiditis; Postpartum thyroiditis
- Iodine; amiodarone-induced thyrotoxicosis
- Levothyroxine excess
- Thyroid carcinoma
Define Graves’ disease
Autoimmune hyperthyroidism due to the presence of TSH receptor antibodies that stimulate T3/4 production.
Grave’s orbitopathy occurs in 1/3
Provide three signs specific for Graves’ disease
- Thyroid acropachy:
- Clubbing and swelling of distal fingers/toes
- Thyroid deropathy:
- Slight pigmented thicken skin
- Leg swelling: typically pretibial
-
Orbitopathy:
- Eye irritation; photophobia; excessive watering
- Red eye/eyelid; lid swelling
- Proptosis; lid lag; eyelid retraction
- Persistent double vision on gaze
- Unexplained deterioration in visual acuity
List five symptoms of hyperthyroidism
- Weight loss; increased appetite; diarrhoea
- Rapid-onset malaise; fever; thyroid pain: subacute thyroiditis
- Agitation; emotional lability; insomnia; irritability; anxiety;
- Palpitations; tremor
- Heat intolerance; increased sweating
- Subfertility; oligomenorrhoea; amenorrhoea; reduced libido
- Polyuria; thirst; generalised itch
- Deterioration of blood glucose control; heart disease
- Goitre
- Eye complaints - Grave’s disease
List three signs of hyperthyroidism
- Agitation; fine tremor
- Warm moist skin; palmar erythema
- Tachycardia; AF; heart failure
- Goitre
- Pruritus; urticaria; vitiligo; diffuse alopecia
- Muscle wasting; proximal myopathy; hyper-reflexia
- Splenomegaly; lymphadenopathy; gynaecomatia
- Pretibial myxoedema (Graves)
- Graves: Thyroid acropachy; dermaopathy; orbitopathy
Name three complications of hyperthyroidism
- Graves’ orbitopathy
- Thyrotoxic crisis/storm
- Oesophageal or tracheal compression
- AF; HF
- Osteoporosis; fractures
What is thyrotoxic crisis?
Rare, life-threatening complication onset by infection; trauma; surgery
- Fever
- Tachycardia; HTN; AF; HF
- Agitation
- Hyperthermia
- Jaundice
- Delirium; coma
Name 3 precipitating factors for thyrotoxic storm
- Stress - MI; stroke; or trauma
- Infection
- Surgery in unprepared patient
- Radioiodine therapy
Outline the management of hyperthyroidism
Beta-blockers for rapid symptom relief
Definitive treatment: first-line case-by-case
- Carbimazole
- Propylthiouracil if pregnant or pancreatitis Hx
- Radioiodine
- Thyroidectomy
What is a fatal side effect of Carbimazole?
Agranulocytosis (0.01%): typically occurs within 3 months
Warn patients to stop and get urgent WCC if showing signs of infection whilst on carbimazole
Stop and do not restart any antithyroid drugs if this occurs
Name two complications of thyroidectomy
- Post-op bleeding
- Tracheal compression
- Asphyxia
- Laryngeal nerve palsy
- Transient (10%) or permanent (<1%) hypocalcemia
What is ‘sick euthyroid syndrome’?
- Wide range of non-thyroidal conditions; starvation; and trauma
- Lead to abnormal TFTs
- TSH normal/low; then high during recovery of acute illness
- Free T4 normal/low/high
- Free T3 typically low due to reduced conversion
- Not due to true dysfunction of HPT axis
What is postpartum thyroiditis (PPT)?
Painless inflammatory autoimmune condition:
- Initial transient thyrotoxicosis or hypothyroidisim
- Thyrotoxicosis may be followed by hypothyroidism
- Return to euthyroid state within one year post-partum
- In women euthyroid prior to pregnancy
Outline the diagnosis and management of a thyroid enlargement with normal thyroid function
- USS for palpable thyroid enlargement or focal nodularity
- Consider FNA
- Treat if breathing difficulties or clinical concern
