Acromegaly glucose tolerance test: what to expect

It is different from a glucose tolerance test used only to investigate diabetes in pregnancy because the laboratory also measures growth hormone. The result is interpreted with your symptoms, examination and other hormone tests; it does not establish a diagnosis by itself.

Growth hormone is released by the pituitary gland in pulses, so a single random level can be misleading. Glucose normally suppresses its release. During this test, blood samples show whether that expected suppression occurs and also track how your blood glucose changes. Failure of growth hormone to suppress can support suspected acromegaly, but an endocrinologist must interpret the pattern alongside an IGF-1 result and your clinical picture.

Follow the testing unit's fasting instructions exactly; plain water is often allowed, but local instructions take priority. Tell the team beforehand if you have diabetes, are pregnant, feel unwell, or take medicines that affect glucose or hormones. Do not stop prescribed medicine unless the clinician arranging the test tells you to.

At the appointment, staff usually place a small cannula in a vein, take a baseline sample, give you a glucose drink and collect further samples while you rest. Bring the request form and a list of medicines. Arrange something to eat afterwards if the unit advises it.

Tell staff immediately during the test if you feel faint, develop marked sweating or shaking, vomit, or cannot finish the drink. After leaving, seek urgent medical help for collapse, severe confusion, breathing difficulty, or swelling of the lips or tongue. Mild nausea or light-headedness can occur, but the team should still know so they can assess you safely.

Ask which medicines to take on the morning of the test, whether your glucose level needs special planning, when results will be available, and how the growth-hormone pattern fits with your IGF-1 level. You can also ask what further assessment would be considered if the result is abnormal or unclear.