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Pentagastrin test

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What is the purpose of the test?

This test is used in the diagnosis and follow-up of patients with a rare type of thyroid cancer. The thyroid gland is at the front of your neck, just below your Adam’s apple. It makes thyroid hormones (chemical signals) which regulate the speed with which your body cells and organs work. Sometimes cancerous nodules develop in the thyroid. These do not usually affect thyroid hormone production.

How long will the test take?

The test will take about 30 minutes.

Who will carry out the test?

The test will be carried out by a specialist nurse or by a phlebotomist (a health care professional trained to take blood). A doctor will supervise the test.

What will I have to do?

Please have nothing to eat or drink for 10 hours before the test.

Is any drug or medicine used during the test?

We will give you an injection of pentagastrin. This similar to a natural protein called gastrin, which is produced in the stomach.

What will happen during the test?

We will check your weight so that we know the correct dose of pentagastrin to give you. A nurse or phlebotomist will put a small plastic tube into a vein in your arm. We will use this to take blood samples and to give you an injection without the need for any more needles. After we have taken the first blood sample, we will give you an injection of pentagastrin. Over the next 15 minutes we will measure your response to the test by taking more blood samples.

What are the possible risks or side-effects of the test?

The pentagastrin injection is likely to cause some side-effects. These might include nausea, discomfort in your stomach, flushing, dizziness, or a racing heart. The side-effects should only last a short time (about 1 minute).

What are the alternatives to the test?

Your endocrinologist will have discussed the indications and reasons for the test with you before recommending it. If you have any concerns, please contact the endocrine specialist nurse.

What will happen after the test?

The blood samples are sent to the laboratory for analysis. This means it can take some time for the results to come back to us. When they have, your endocrinologist will discuss them with you.

Who do I contact if I have any questions?

Endocrine Specialist Nurses

Royal Sussex County Hospital
Endocrine specialist nurse
01273 696955 extension 64379

Princess Royal Hospital, Haywards Heath
Endocrine specialist nurse
01444 441881 extension 65660

If you have any urgent or emergency questions then your GP can advise you or they will contact the hospital on your behalf.

Patient self-help groups and further information: British Thyroid Foundation

    This information is intended for patients receiving care in Brighton & Hove or Haywards Heath.

    The information in this leaflet is for guidance purposes only and is in no way intended to replace professional clinical advice by a qualified practitioner.

      Publication Date: July 2021

      Review Date: April 2024

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