GUCY2C and irritable bowel syndrome: Two GUCY2C agonists recently received FDA-approval for the treatment of chronic idiopathic constipation and constipation-predominant irritable bowel syndrome: linaclotide (LinzessTM) (23–25) an ST analog, and plecanatide (TrulanceTM) (26, 27) an analog of the endogenous GUYC2C ligand, uroguanylin (discussed below).