Growth hormone suppression test

Investigation Protocol

Indication

Diagnosis and monitoring of patients with suspected acromegaly.

Preparation

Glucose solution is best prepared in advance as glucose dissolves better in warm water but is more palatable when cold. On the day prior to the test, dissolve 75 grams of anhydrous glucose (82.5 grams of glucose monohydrate, obtainable pre-weighed from pharmacy) in warm water and store in a fridge overnight.

The patient must be fasted from midnight (sips of water only). However, medications should continue as normal unless otherwise instructed by the consultant.

Procedure

Insert an indwelling cannula gauge 20 with a three-way tap. Using the vacutainer connector system or a syringe, fill one plain clotted bottle for growth hormone, and one fluoride oxalate bottle for glucose. Label with patient identification and label the tubes -10minutes.

Flush the cannula with 2mls 0.9% sodium chloride after each blood sample; withdraw 2mls blood and discard to remove any trace of the sodium chloride flush prior to taking each sample.

Allow the patient to rest for 10 minutes before taking further samples into a further plain clotted bottle and a fluoride oxalate bottle. Label both with patient identification, date and time=0 minutes.

Give the glucose solution to drink (within 10 minutes). Some patients may feel sick and have vaso-vagal symptoms during this test. It is therefore advisable that they be on a couch or bed during the test where they may rest and elevate legs should this occur. 

Collect further blood samples as above for growth hormone and glucose, every 30 minutes for 2.5 hours, making sure that each sample is clearly labelled with the patient identification, date and time of sample (i.e. 30, 60, 90, 120,150 minutes). Remove cannula.

The patient may then have a meal and go home.

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Patient information sheet

Growth hormone suppression test

Your doctor has referred you to have a growth hormone suppression test, which is performed over a two and half hour period. This is to establish whether your pituitary gland is producing too much growth hormone.

During the test blood samples will be taken at half hourly intervals and 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 your arm at the start of the test. Baseline samples of blood to measure glucose (sugar) levels and growth hormone levels are taken. Following a 10-15 minute rest further samples of blood are taken and then you will be given a drink of chilled glucose solution, which you will be asked to drink within ten minutes. You will be resting on a reclining chair in the unit for the duration of the test.

Please come fasting, i.e. nothing to eat or drink from midnight except sips of water, and please avoid smoking on the day of the test. You can take all your normal medications as usual, but please bring them with you for us to document. You will be offered a drink and something to eat at the end of the test.

If you have diabetes please let us know before you attend for this test.

You should expect your stay at the hospital to last about three and 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. You should be able to undertake normal activities after the test is finished and it should not interfere with your ability to drive home.

If you have any queries about the test, please contact

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