Hypothyroidism Flashcards

1
Q

Definition

A

The clinical syndrome resulting from insufficiency secretion of thyroid hormones

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2
Q

Aetiology/Risk factors (primary)

A

· PRIMARY HYPOTHYROIDISM (decreased thyroid hormone production)

o Acquired
· Hashimoto's thyroiditis (autoimmune)
· Iatrogenic (post-surgery, radioiodine, hyperthyroid medication)
· Severe iodine deficiency
· Iodine excess (Wolff-Chaikoff effect)
· Thyroiditis

o Congenital
· Thyroid dysgenesis
· Inherited defects in thyroid hormone biosynthesis

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3
Q

Aetiology/Risk factors (secondary)

A

· SECONDARY HYPOTHYROIDISM (5% of cases)

o Pituitary and Hypothalamic Disease - resulting in reduced TSH and TRH and, hence, reduced stimulation of thyroid hormone production

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4
Q

Epidemiology

A

· 0.1-2% of adults
· 6 x more common in FEMALES
· Most common age of onset > 40 yrs
· Iodine deficiency is seen in mountainous areas (e.g. Himalayas)

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5
Q

Presenting symptoms

A
· INSIDIOUS onset
· Cold intolerance
· Lethargy
· Weight gain
· Reduced appetite
· Constipation
· Dry skin
· Hair loss
· Hoarse voice
· Mental slowness
· Depression
· Cramps
· Ataxia
· Paraesthesia
· Menstrual disturbance (irregular cycles, menorrhagia)
· History of surgery or radioiodine therapy for hyperthyroidism
· Personal/family history of other autoimmune conditions (e.g. Addison's, type 1 diabetes mellitus)
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6
Q

Presenting symptoms (myxoedema coma)

A

· Myxoedema coma (severe hypothyroidism usually seen in the elderly):

o Hypothermia
o Hypoventilation
o Hyponatraemia
o Heart failure
o Confusion
o Coma
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7
Q

Signs on physical examination

A

· Hands
o Bradycardia
o Cold hands

· Head/Neck/Skin
o Pale puffy face
o Goitre
o Oedema
o Hair loss
o Dry skin
o Vitiligo

· Chest
o Pericardial effusion
o Pleural effusion

· Abdomen
o Ascites

· Neurological
o Slow relaxation of reflexes
o Signs of carpal tunnel syndrome

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8
Q

Investigations

A

· Bloods

o TFTs
o FBC - may show normocytic anaemia
o U&Es - may show low sodium
o Cholesterol - may be high

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9
Q

Management plan (chronic)

A

o Levothyroxine (25-200 mcg/day)

· IMPORTANT: rule out underlying adrenal insufficiency before starting thyroid hormone replacement

· Thyroid hormone replacement in the context of adrenal insufficiency can precipitate an Addisonian crisis

· Adjust dose based on clinical picture and TFTs

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10
Q

Management plan (myxoedema coma)

A
o Oxygen
o Rewarming
o Rehydration
o IV T4/T3
o IV hydrocortisone
o Treat underlying cause (e.g. infection)
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11
Q

Possible complications

A

· Myxoedema coma

· Myxoedema madness (psychosis with delusions and hallucinations or dementia)

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12
Q

Prognosis

A

· Lifelong levothyroxine is required

· Myxoedema coma mortality = 80%

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