Peri-operative Dynamics of the Growth Hormone Axis in Subjects With Acromegaly

Acromegaly is a rare disorder characterized by excessive production of growth hormone most often by a pituitary adenoma. A pituitary adenoma is a tumor, almost always benign or non-cancerous, that grows on the pituitary, a small gland located at the base of the brain. Treatment of acromegaly usually involves surgery, medication, or radiation, but can involve a combination of these three treatments. Subjects for this study will be recruited if they are: 1. Adults, male or female, between the ages of 18-90. 2. Have been diagnosed with acromegaly, based on elevated levels of growth hormone, IGF-I (a hormone made in response to growth hormone), and a pituitary adenoma visualized on an MRI. 3. Patients would have already agreed to have their acromegaly treated with surgery prior to study entry. Subjects will have measurements of growth hormone using an oral glucose tolerance test (OGTT), IGF-I, free IGF-I and levels of IGF binding proteins at four time points after their pituitary surgery: Day 1, Day 42 (6 weeks), Day 84 (12 weeks), and day 365 (1 year). Subjects will also have an MRI of the pituitary done at 12 weeks and 1 year. OGTT and IGF-I are routinely measured to assess whether or not a person is cured of their acromegaly. An MRI of the pituitary is routinely done at 12 weeks and 1 year after surgery to assess the results of surgery. Free IGF-I and IGF binding proteins are not routinely measured after surgery, but are being done to see if they relate more strongly to disease activity than IGF-I and growth hormone. OGTT and the IGF-I binding proteins are not routinely measured on the day after surgery, but are being done to examine the predictive ability of these tests at a very early time after surgery. Data obtained from these tests will be compared to the data gathered at the 1 year time point. IGF-I and growth hormone will be measured by a commercial clinical lab, Quest Diagnostics, for clinical decision-making at the time of service. IGF-I and growth hormone will also be measured using other methods to attempt to investigate the variability of these hormones when different assays are used.