Investigating Thyroid Function

Why focus on thyroid function tests? Investigating Thyroid Function
When to test?
Screening patients at increased risk / asymptomatic patients
Which test should be used?
Limitations of thyroid function tests
Monitoring
Thyroid tests in the pregnant patient
Sick euthyroid syndrome
Thyroid cancer
The effects of drugs on thyroid function
GP and laboratory communication
Range of tests available
Thyroid function
References
See also TSH vs FT4: Reminder May 2007
Full colour PDF of the “Investigating Thyroid Function” POEM.
 Printer friendly PDF.
Download a powerpoint presentation of the key points.

Why focus on thyroid function tests?

  • TSH and FT4 are commonly ordered tests.
  • TSH and FT4 (and FT3) are frequently ordered simultaneously as “thyroid function tests”.
  • The choice of “thyroid function test” has changed over the last 10-15 years; previously FT4 has been the most popular test, now TSH is favoured.
  • It is now possible to make recommendations based on current understanding.

bpacnz recommends

  1. Asymptomatic patients are not screened for thyroid dysfunction.
  2. TSH is used as the sole test of thyroid function in most situations.

Why do we make these recommendations?

  1. Patients with no symptoms of thyroid disease and no obvious risk factors have a low likelihood of thyroid disease.
  2. In most situations, TSH is the more sensitive indicator of thyroid status. If further thyroid function tests are indicated they can be subsequently added by the laboratory, or the GP usually without the need to retest the patient.
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