Glucagon is a polypeptide hormone identical to human glucagon that increases blood glucose and relaxes smooth muscle of the gastrointestinal tract. Glucagon is synthesized in a special non-pathogenic laboratory strain of Escherichia coli bacteria that has been genetically altered by the addition of the gene for glucagon. Glucagon generally elevates the concentration of glucose in the blood by promoting gluconeogenesis and glycogenolysis. Glucagon also decreases fatty acid synthesis in adipose tissue and the liver, as well as promoting lipolysis in these tissues, which causes them to release fatty acids into circulation where they can be catabolised to generate energy in tissues such as skeletal muscle when required. Glucose is stored in the liver in the form of the polysaccharide glycogen, which is a glucan (a polymer made up of glucose molecules). Liver cells (hepatocytes) have glucagon receptors. When glucagon binds to the glucagon receptors, the liver cells convert the glycogen into individual glucose molecules and release them into the bloodstream, in a process known as glycogenolysis. As these stores become depleted, glucagon then encourages the liver and kidney to synthesize additional glucose by gluconeogenesis. Glucagon turns off glycolysis in the liver, causing glycolytic intermediates to be shuttled to gluconeogenesis. Glucagon also regulates the rate of glucose production through lipolysis. Glucagon induces lipolysis in humans under conditions of insulin suppression (such as diabetes mellitus type 1). Glucagon increases blood glucose concentration and is used in the treatment of hypoglycemia. Glucagon administered through a parenteral route relaxes smooth muscle of the stomach, duodenum, small bowel, and colon. Glucagon is also indicated as a diagnostic aid in the radiologic examination of the stomach, duodenum, small bowel, and colon when diminished intestinal motility would be advantageous.

More than a century ago, Sir Henry Dale demonstrated that a component of the pituitary causes contractions of the mammalian uterus, hence his coining the term “oxytocic,” derived from the Greek for “quick birth,” for its activity. The discovery that a component of the pituitary causes milk secretion followed within a few years. By 1930, oxytocin was separated from vasopressin into pitocin and pitressin, respectively, at Parke Davis and made available for research. That a single peptide was responsible for these uterine and mammary actions was definitively confirmed upon the sequencing and synthesis of the peptide, 9 amino acids in length. Vincent du Vigneaud was awarded a Nobel Prize for this work. Oxytocin is indicated for the initiation or improvement of uterine contractions, where this is desirable and considered suitable for reasons of fetal or maternal concern, in order to achieve vaginal delivery. Oxytocin is indicated to produce uterine contractions during the third stage of labor and to control postpartum bleeding or hemorrhage. Uterine motility depends on the formation of the contractile protein actomyosin under the influence of the Ca2+- dependent phosphorylating enzyme myosin light-chain kinase. Oxytocin promotes contractions by increasing the intracellular Ca2+. Oxytocin has specific receptors in the myometrium and the receptor concentration increases greatly during pregnancy, reaching a maximum in early labor at term. The Oxytocin receptor is a typical class I G protein-coupled receptor that is primarily coupled via G(q) proteins to phospholipase C-beta. The high-affinity receptor state requires both Mg(2+) and cholesterol, which probably function as allosteric modulators. The agonist-binding region of the receptor has been characterized by mutagenesis and molecular modeling and is different from the antagonist binding site. The function and physiological regulation of the Oxytocin system is strongly steroid dependent.

N-(2-Bromophenyl)-9-Methyl-9-Azabicyclo[3.3.1]Nonan-3-Amine (also known as AT-1001) is a high-affinity and highly selective ligand at α3β4 nicotinic cholinergic receptors (nAChRs) that was reported to decrease nicotine self-administration in rats. AT-1001 has a single-digit nanomolar binding affinity for the α3β4 nAChR and over 100-fold selectivity over the α4β2 nAChR and α7 nAChR in competition binding experiments. In electrophysiological experiments, AT-1001 had partial agonist activity at the α3β4 nAChR, evoking 35% of maximum ACh response, and at the same doses, produced desensitization of the ACh response, effectively acting as a functional antagonist at the α3β4 nAChR. Interestingly, AT-1001 also selectively decreased self-administration of cigarette smoke extract (CSE), an aqueous extract of cigarette smoke components, without altering natural food intake, when administered systemically to rats trained to self-administer CSE

AC-2592 (glucagon-like peptide 1, or GLP-1) was being in development by Amylin Pharmaceuticals for the treatment of severe congestive heart failure. AC-2592 is a glucagon like peptide 1 receptor agonist.

Iodide I-131 (as Sodium iodide I-131) is a radioisotopic drug used for the treatment and palliation of thyroid malignancy. Iodine-131 is notable for causing mutation and death in cells that it penetrates, which is due to its mode of beta decay. Iodide I-131 can be detected by gamma cameras for diagnostic imaging, however, it is rarely administered for diagnostic purposes only, imaging will normally be done following a therapeutic dose. Major uses of 131I include the treatment of thyrotoxicosis (hyperthyroidism) due to Graves' disease, and sometimes hyperactive thyroid nodules (abnormally active thyroid tissue that is not malignant). Iodine-131, in higher doses than for thyrotoxicosis, is used for ablation of remnant thyroid tissue following a complete thyroidectomy to treat thyroid cancer. The 131I isotope is also used as a radioactive label for certain radiopharmaceuticals that can be used for therapy, e.g. 131I-metaiodobenzylguanidine for imaging and treating pheochromocytoma and neuroblastoma. Because of the carcinogenicity of its beta radiation in the thyroid in small doses, I-131 is rarely used primarily or solely for diagnosis. Instead, the more purely gamma-emitting radioiodine iodine-123 is used in diagnostic testing. The longer half-lived iodine-125 is also occasionally used when a longer half-life radioiodine is needed for diagnosis, and in brachytherapy treatment, where the low-energy gamma radiation without a beta component makes iodine-125 useful.

Angiotensin III (Ang III) is a bioactive heptapeptide that is formed from the degradation of the Angiotensin II peptide by aminopeptidase A. In peripheral Angiotensin systems, Angiotensin II is the main effector peptide in the systemic circulation, although exogenous Angiotensin III can be as potent as Angiotensin II in, for example, stimulating aldosterone secretion or inhibiting renin release. In the rat brain, Angiotensin III was found to be equipotent with Angiotensin II as a pressor agent or dipsogen and was bound as avidly to the nervous system as Angiotensin II. Angiotensin receptor subtype AT1 has the greater affinity towards Angiotensin II and is also responsive to Angiotensin III, while the AT2 receptor subtype appears to be more sensitive to Angiotensin III but less responsive to Angiotensin II. Angiotensin III enhances blood pressure, vasopressin release and thirst when it is centrally administrated. Angiotensin III infusion increases blood pressure in healthy volunteers and hypertensive patients as well as augments aldosterone release. Although Angiotensin III does not change renal function in humans, it induces natriuresis in AT, receptor-blocked rats likely by binding to AT2 receptors. In addition, in cultured renal cells, this peptide stimulates the expression of many growth factors, proinflammatory mediators, and extracellular matrix proteins.

Peginesatide (trade name Omontys, formerly Hematide), developed by Affymax and Takeda, is an erythropoietic agent, a functional analog of erythropoietin. It was approved by the U.S. Food and Drug Administration for treatment of anemia associated with chronic kidney disease (CKD) in adult patients on dialysis. Peginesatide is a synthetic peptide, attached to polyethylene glycol ("PEGylated"). It mimics the structure of erythropoietin, the human glycoprotein which promotes red blood cell development. Peginesatide binds to and activates the human erythropoietin receptor and stimulates erythropoiesis in human red cell precursors in vitro.