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Thyrotropin releasing hormone (TRH) test

Patient information A-Z

What is a thyrotropin releasing hormone (TRH) test?

Your doctor has referred you for a thyrotropin releasing hormone (TRH) test. This test assesses how your pituitary gland (a hormone-producing gland at the base of your brain) responds to an injection of a hormone made naturally in the body called TRH. In response to the TRH injection, the pituitary gland usually produces another hormone called thyroid stimulating hormone (TSH). TSH in turn controls how much thyroid hormone your thyroid gland makes. Overall, this test provides information on hormones that control thyroid gland function.

The timing of the test is important, so please attend at the time specified on your appointment letter. If you are unable to attend your appointment, please contact the Endocrine Unit on 01223 217848 to rearrange it.

Do I need to prepare for the test?

No. You can eat and drink as normal on the day of the test.

What happens during the test?

On arrival at the endocrine investigation unit you will be made comfortable on a bed. To allow us to take blood samples at regular intervals a fine plastic tube, called a cannula, will be inserted into a vein in your arm.

How long will the test take?

About an hour is needed while blood samples are taken but please allow an hour and a half as you may want to rest after the test. Very occasionally, a longer test is performed with blood sampling up to three hours following the TRH injection, however if your doctor wishes you to have this prolonged version of the test, it will have been discussed with you in clinic.

Will I experience any side effects?

Occasionally, people experience nausea, light-headedness, flushing, palpitations, headache and a desire to pass urine, though these symptoms usually last under 10 minutes.
If you think you may be pregnant, please let us know when you receive this information leaflet.

When will I get my results?

Results will be discussed at your next clinic appointment. (Note: they cannot be given out over the telephone.)

Any other questions?

If you have any questions, please contact the Endocrine Unit.

Parking: Discounted parking is available for patients attending clinic appointments taking more than three hours. Please present your appointment letter to receive this discount.

Food and drink: There is a coffee shop in the treatment centre atrium and other food and drink facilities in the main hospital concourse.

We are smoke-free

Smoking is not allowed anywhere on the hospital campus. For advice and support in quitting, contact your GP or the free NHS stop smoking helpline on 0800 169 0 169.

Other formats

Help accessing this information in other formats is available. To find out more about the services we provide, please visit our patient information help page (see link below) or telephone 01223 256998.

Contact us

Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge

Telephone +44 (0)1223 245151