<prompt> cGMP is second messenger for which hormone sSomatostatinAtrial natruretic factorAngiotensin IINitric Oxide NO  <response>: cGMP exist in two forms Figure 2-29. One form has an extracellular amino-terminal domain that is a receptor, a single transmembrane domain, and a cytoplasmic poion with guanylyl cyclase catalytic activity. Three such guanylyl cyclases have been characterized. Two are receptors for atrial natriuretic peptide ANP; also known as atrial natriuretic factor, and a third binds an Escherichia coli enterotoxin and the gastrointestinal polypeptide guanylin.Ref: Ganongs review of medical physiology 23rd Edition page no.57 