Oral Glucose Tolerance Test with Growth Hormone Levels

You are booked to come in for an : Oral Glucose tolerance test (OGTT) with Growth hormone levels

What is an OGTT with GH levels?

An OGTT with GH levels looks to see if your body is making too much of a hormone called growth hormone (GH). A hormone is a chemical which is made in one part of the body but passes into the bloodstream and has effects on other parts of the body. GH is produced by your pituitary gland (a small gland that lies just under the brain.) GH has important effects on growth in childhood and influences adult body composition and the functioning of several body systems. Overproduction of GH in adulthood is called acromegaly.

Measuring a single level of GH is not helpful as the body produces GH in pulses. GH tends to increase blood sugar and conversely, when things are working normally, a fixed dose of sugar by mouth lowers GH to undetectable levels. In acromegaly, the GH levels remain high (or may even increase) after a dose of sugar by mouth. This test looks at what happens to both your blood sugar levels and growth hormone levels after drinking a sugar solution.



How should I prepare for the test?

You should fast overnight before the test, drinking only water from midnight. You should take your medications as usual the day before the test unless your doctor has advised you not to.



What will happen during the test?

You should come to the ward on the date of the test, by 9am. You will have a bed to lie down in throughout the test. A cannula (a small needle with a tube attached for taking blood samples) will be placed in a vein in your arm. After the first blood sample has been taken from the cannula you will be given a sugary drink. Further blood samples will be taken from the cannula at half hour intervals for 2 hours. Once the test is completed, the cannula will be removed and you will be able to go home.



What happens after the test?

When the results of the blood tests are available they will be reviewed by the endocrinology team. You will be notified by letter and your GP will also be informed of the results. If there are any changes to be made to your treatment or further tests that need to be organized, these will be outlined in the letter or someone from the department may contact you by telephone.



What if I have any questions?

You will see a doctor on the day of your test who should be able to answer your queries. If you have any questions before or after your test please leave a message and contact number with the endocrine department at the Hospital where your test is booked. Someone will call you back to discuss things.