Thyroid emergencies

Myxoedema Coma

A myxoedemic foot.

Definition

Failure of the body's adaptation to a lack of thyroxine resulting in a coma.

Epidemiology

It doesn't happen very often happen, especially as most people who have hypothyroidism are monitored really well. However, it has a mortality of 50%.

Pathophysiology

In long-standing hypothyroidism, the body has to make adaptations (i.e. it gets used to) in light of the low levels of thyroxine. However, eventually, it basically gives in and goes into coma. Which is bad. This coma is called a myoedema coma because

Risk Factors

Long-standing hypothyroidism is the most important. Here are a bunch of precipitants:

• Hypothermia
• Infections - influenza, pneumonia, UTI
• Medication - amiodarone, anaesthesia, beta blockers, diuretics, CNS drugs, lithium, phenytoin, rimfampicin

They're the main ones. Here are some others:

• GI haemorrhage
• hypoglycaemia
• CVA
• Trauma - surgery, burns, accidents
• Respiratory depression
• CO₂ retention

Clinical Features

Same as for hypothyroidism. However, there are two key extra ones which are probably obvious:

1. Coma
2. Oedema in the hands, face and feet.

• Protruding tongue (macroglossia), ptosis (droopy eyelid).

Myxoedema coma is rare - this of other causes of coma first.

Investigations

• TFTs - TSH is always raised. T₃ & T₄ are always reduced.
• U+Es, blood sugar, FBC
• Oxygen saturation, Blood gases, Blood culture and Lipid profile
• ECG
• CXR
• Serum cortisol - (for hypopituitarism)

Management

• General measures - ABC, admission to [[intensive care] and general supportive stuff.
• Then - T₄ 100-500mcg iv, antibiotics and corticosteroids.

Prognosis

50% mortality. So, quite bad.