Arginine-GHRH test

Investigation Protocol

Indication

Assessment of  growth hormone reserve when insulin stress test is contraindicated.

Preparation and precautions

Patients should be fasting from midnight (water only). Warn the patient that they may well experience flushing, nausea, an unusual taste and a transient drop in blood pressure during the test.

Procedure

Wiegh the patient without shoes on and take baseline pulse and blood pressure recordings. Insert a cannula gauge 20 with a three-way tap into each arm. Allow the patient to rest for 15 minutes. Monitor the patient's pulse and BP every 15 minutes until +150 minutes into the test and every 30 minutes thereafter to +240 minutes.  Using a syringe or the vacutainer connector system, fill one plain clotted bottle for growth hormone and baseline IGF-I level from cannula 1, and label this -15 minutes. Label with patient identification, date and write time=0 minutes.

Using the separate cannula 2, give GHRH 1mcg/kg (maximum dose 100mcg) as a bolus injection and flush with 10ml normal saline. Then start an infusion of 0.5g/kg arginine (maximum dose 30g/300ml) over 30 minutes into cannula 2, as prescribed by the requesting doctor.

Take further blood samples from cannula 1 as above for GH only immediately after the infusion ends and label this + 30 minutes. Take further samples, also from cannula 1 at 45, 60, 90, 120 and 150 minutes after the start of the infusion. Mark the patient’s details, date and time of samples on each bottle. Each time samples are taken, flush the cannula with 2mls 0.9% sodium chloride and prior to taking blood samples, withdraw 2mls and discard to remove any trace of the sodium chloride flush.

The patient should remain fasting during the test but can sip water. After the 150 minute samples have been taken, both cannulae can be removed, and the patient offered a meal.

Patients should remain resting in bed and have pulse and BP monitored every 30 minutes until +240 minutes. The patient may then go home.

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Patient information sheet

Arginine-GHRH test

Your doctor has referred you for an arginine-GHRH test to measure your growth hormone levels after stimulation. This hormone is controlled by the pituitary gland.

Please come fasting, i.e. nothing to drink from midnight except sips of water, though you can take your medication as usual. You will be offered a drink and something to eat at the end of the test. Smoking should also be avoided on the day of the test.

During the test blood samples will be taken at 15-30 minute intervals over a four hour period. To allow this to happen easily with the minimum of discomfort for you, we will be inserting a small tube (a cannula) into a vein in each arm at the start of the test. After some baseline samples of blood have been taken, you will be given an infusion of GHRH followed by arginine, which will stimulate your body to release cortisol and growth hormone so it can be measured. You will be able to relax in reclining chair in the unit.

Arginine may cause a temporary drop in blood pressure so this will be monited throughout the test and for 90 minutes afterwards. GHRH can also cause facial flushing, nausea and a strange taste in the mouth, though all of these side effects wear off very quickly. Most people have completely recovered by the end of the test, and so it is not necessary for someone else to drive you to and from the appointment unless you want them to. You should expect your stay at the hospital to last at least four and a half hours.

You may wish to bring a book or magazine to read. We do have a radio, or you can access Patientline; alternatively you may like to bring your own personal radio/cd player (please bring your own headphones). You may bring someone to stay with you during the test but there is not enough space for more than one person.

Children are discouraged, as this can be disruptive to other patients. However, if this poses a particular problem for you please discuss this with the senior nurse in the unit. 

If you have any queries about the test, please contact

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