Blood tests for acromegaly

The oral glucose tolerance test, or OGTT, is generally done in the morning and will require you to fast for 8 to 10 hours before the test.   This includes having no food or fluids such as tea, coffee or fruit juice.  You may however have sips of water if you are thirsty.

When you go in for the test, a blood sample will be taken and you will be given a glucose (‘sugary’) liquid that you will need to drink within 5 minutes.

A blood sample will be collected 1 hour and 2 hours after you finished drinking the glucose liquid.

In people without acromegaly, the glucose in the drink will normally cause growth hormone levels to fall.  If your body is making too much of the hormone, these levels will not go down enough, which helps confirm the diagnosis of acromegaly.

A reliable way to track growth hormone in the body is by measuring the level of IGF-1 (insulin growth factor) in the blood.

IGF-1 measurement is the most accurate screening blood test.  In most cases, a high IGF-1 level suggests that you have acromegaly.

IGF-1 measurement is often done at the same time as an oral glucose tolerance test.