TRH Test

Get a TRH vial in a pharmacy. The vial may also be purchased at the laboratory.

The patient must be fasting and have not drunk any coffee (only water is authorised). They must rest for the entirety of the test.

Minor side effects may occur after the injection, they will however fade within 2 or 3 minutes.

The TRH test involves administration of a small amount of TRH intravenously, following which levels of TSH will be measured at several subsequent time points using samples of blood taken from a peripheral vein.

First, blood is drawn and a baseline TSH level is measured. Then, TRH is administered via a vein (200 microg).

Based on the request of the prescribing physician, two additional samples are taken:

  • Either after 20 then 60 minutes.
  • Or after 15 then 30 minutes.

And the following is measured:

  • TSH assay
  • And/or prolactin
  • And/or (more rarely) GH, FSH, LH and alpha subunit

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