Hypothyroxinaemia (euthyroid)

Last updated: Friday, 06, August, 2010
Key InformationAppropriate Tests

Sick euthyroid syndrome 

The interpretation of thyroid function tests in an acutely ill patient is difficult and the tests should generally be reserved for when there is clinical suspicion of myxoedema coma or thyroid crisis.

TSH levels are variable and thyroxine (free) may be low; these findings are seldom of clinical significance.

Thyroid status should be assessed when the patient is otherwise well.


  • Phenytoin
  • Diazepam

The effect is seen only when thyroxine (total) is measured, and is of no clinical significance.

Thyroxine (free) is normal.