Tissue Biomarker for Pegvisomant Action

Acromegaly is a disease of the pituitary gland that involves the overproduction of growth
hormone. The drug works by blocking the binding of growth hormone to growth hormone
receptors found in tissues throughout the body. Human studies have evaluated the reduction
of IGF-I levels in the blood following pegvisomant treatment, however, no studies have
evaluated IGF-I levels in tissues following pegvisomant administration. In this study, we
will test a novel tissue biomarker for pegvisomant action, distinct from measuring IGF-I
levels in the blood. To this end, we will determine if administration of pegvisomant
modifies the expression of IGF-I, IGF-I receptor, growth hormone receptor and GH- and
IGF-i-dependent signaling molecules in the colon tissue of patients with acromegaly.