Acromegaly is a disease of the pituitary gland that involves overproduction of growth hormone. Pegvisomant works by blocking binding of GH to receptors found in tissues throughout the body. Human studies have evaluated pegvisomant action by measuring reduction of IGF-I levels in the blood. However, no studies have evaluated the effects of blocking GH receptors in tissues. In this study, we will study tissue biomarkers for pegvisomant action in GH and IGF-I dependent signaling pathways in colon tissue of patients with acromegaly treated with pegvisomant.

Inclusion Criteria:

• Diagnosis of acromegaly established on the basis of symptoms and signs at presentation, evidence of a pituitary adenoma on MRI, elevated serum concentrations of IGF1 (>1.3 X ULN), and inadequate GH suppression (>0.4 ng/mL) following OGTT
• Candidates to receive pegvisomant therapy following pituitary adenoma surgery, or intolerant of other medical treatments or had not undergone previous therapy
• Normal LFTs before treatment
• Dynamic testing of the pituitary axis and, if applicable, appropriate hormone replacement

Exclusion Criteria:

• Treatment with a long-acting SRL within 12 weeks before enrollment
• Presence of a macroadenoma with visual field defects as a result of chiasmatic compression
• Clinically significant hepatic abnormalities and/or AST or ALT >3 X ULN on screening
• Known hypersensitivity to any of the test materials or related compounds
• History of, or known current, problems with alcohol or drug abuse
• Any mental condition rendering the patient unable to understand the nature, scope, and possible consequences of the study, and/or evidence of an uncooperative attitude

8 months

Small sample size due to rare patient population