PEGVISOMANT IS A GROWTH HORMONE-RECEPTOR ANTAGONIST USED FOR THE TREATMENT OF ACROMEGALY. PEGVISOMANT SELECTIVELY BINDS TO GROWTH HORMONE (GH) RECEPTORS ON CELL SURFACES, WHERE IT BLOCKS THE BINDING OF ENDOGENOUS GH, AND THUS INTERFERES WITH GH SIGNAL TRANSDUCTION. INHIBITION OF GH ACTION RESULTS IN DECREASED SERUM CONCENTRATIONS OF INSULIN-LIKE GROWTH FACTOR-I (IGF-I), AS WELL AS OTHER GH-RESPONSIVE SERUM PROTEINS, INCLUDING IGF BINDING PROTEIN-3 (IGFBP-3), AND THE ACID-LABILE SUBUNIT (ALS).