Pegvisomant With Glucagon Test to Assess for Adult Growth Hormone Deficiency

Hypothesis: Pegvisomant combined with the glucagon stimulation test (GST) can improve the accuracy of this test when used to diagnose adult GH and cortisol (steroid hormone)insufficiency. Study aims: Diagnosing GH and cortisol deficiency in adults requires a special test. At present, the insulin tolerance test (ITT) is considered the test of choice. However, this test is difficult to perform as it involves giving insulin through the veins to decrease blood sugars to very low levels, and this can be unpleasant, and cannot be performed in elderly adults and in those with a history of heart disease, seizure disorders or stroke. For this reason there is an urgent need for an alternative reliable test. At present, the GST is considered the alternative test to the ITT but its accuracy in obese patients and in those with diabetes remains unclear. Pegvisomant is a medication that can increase GH production in the body. The purpose of this study is to find out if combining pegvisomant with the GST can help improve the accuracy of this test so that it is comparable with the ITT in diagnosing adult GH and cortisol insufficiency. Study design: Subjects will be recruited from the Oregon Health \& Science University Dynamic Endocrine Testing Unit. A written informed consent will be obtained and a screening interview will be carried out. During the screening interview, the study will be explained to the subject in detail. For women of child-bearing age, a pregnancy test will be performed. The subjects will then take part in three studies on separate days: (1) GST; (2) pegvisomant (1 mg/kg) injection into the abdomen 3 days before the glucagon stimulation test (ii) insulin tolerance test. For the GST, glucagon will be injected into the muscle and blood draws will be performed every 30 mins for 240 mins. For the insulin tolerance test, a blood draw will be performed and insulin will be given into the vein followed by blood draws every 15 mins for 120 mins. The data from all three studies will be analyzed in the study where the peak growth hormone and cortisol levels for all three tests will be compared. A questionnaire will be used at the end of the study for the subjects to rank the level of preference of the three tests. The data of the study will be analyzed using a computer statistical program where the identity of the subjects will be coded to maintain confidentiality.