Human secretin is a gastrointestinal peptide hormone that regulates secretions in the stomach, pancreas, and liver. Synthetic human secretin displays equivalent biological activity and properties as naturally occurring secretin. Acetate salt of synthetic secretin was marketed under the name ChiRhoStim. ChiRhoStim is indicated for the stimulation of pancreatic secretions, including bicarbonate, to aid in the diagnosis of pancreatic exocrine dysfunction, for the gastrin secretion to aid in the diagnosis of gastrinoma. ChiRhoStim is also used for the pancreatic secretions to facilitate the identification of the ampulla of Vater and accessory papilla during endoscopic, retrograde cholangiopancreatography (ERCP). When secretin binds to secretin receptors on pancreatic duct cells it opens cystic fibrosis transmembrane conductance regulator (CFTR) channels, leading to secretion of bicarbonate-rich-pancreatic fluid.

Ziconotide (PRIALT; SNX-111) is a neuroactive peptide, which was approved by FDA in 2004 for the management of severe chronic pain in adult patients for whom intrathecal therapy is warranted, and who are intolerant of or refractory to other treatment, such as systemic analgesics, adjunctive therapies, or intrathecal morphine. Ziconotide acts as a selective N-type voltage-gated calcium channel blocker, which leads to a blockade of excitatory neurotransmitter release from the primary afferent nerve terminals.

Triptorelin is a synthetic decapeptide agonist analog of luteinizing hormone releasing hormone (LHRH). It works by decreasing the production of certain hormones, which reduces testosterone levels in the body. Animal studies comparing triptorelin to native GnRH found that triptorelin had 13 fold higher releasing activity for luteinizing hormone, and 21-fold higher releasing activity for follicle-stimulating hormone. Triptorelin is indicated for the palliative treatment of advanced prostate cancer.

Teriparatide was manufactured under the brand name FORTEO. FORTEO contains recombinant human parathyroid hormone (1-34), [rhPTH(1-34)], which has an identical sequence to the 34 N-terminal amino acids (the biologically active region) of the 84-amino acid human parathyroid hormone, that regulates calcium and phosphate in the body. FORTEO is indicated for the treatment of postmenopausal women with severe osteoporosis who are at high risk of fracture or who have failed or are intolerant to previous osteoporosis therapy. In addition, Forteo is used for the treatment of osteoporosis associated with sustained systemic glucocorticoid therapy in men and women who are at increased risk for fracture. The biological actions of teriparatide is mediated through binding to specific high-affinity cell-surface receptors. Teriparatide is not expected to accumulate in bone or other tissues.

Calcitonin-salmon is a polypeptide hormone secreted by the parafollicular cells of the ultimobranchial gland of salmon fish. Calcitonin-salmon Nasal Spray is a polypeptide of 32 amino acids manufactured by recombinant DNA technology and is identical to calcitonin produced by salmon fish or chemical synthesis. Calcitonin acts primarily on bone, but direct renal effects and actions on the gastrointestinal tract are also recognized. Calcitonin-salmon appears to have actions essentially identical to calcitonins of mammalian origin, but its potency per mg is greater and it has a longer duration of action. The actions of calcitonin on bone and its role in normal human bone physiology are still not completely elucidated, although calcitonin receptors have been discovered in osteoclasts and osteoblasts. Single injections of calcitonin cause a marked transient inhibition of the ongoing bone resorptive process. With prolonged use, there is a persistent, smaller decrease in the rate of bone resorption. Histologically, this is associated with a decreased number of osteoclasts and an apparent decrease in their resorptive activity. In vitro studies have shown that calcitonin-salmon causes inhibition of osteoclast function with loss of the ruffled osteoclast border responsible for resorption of bone. Calcitonin-salmon Nasal Spray is indicated for the treatment of postmenopausal osteoporosis in females greater than 5 years postmenopause with low bone mass relative to healthy premenopausal females.

Cosyntropin (ACTH (1–24)) is a synthetic peptide that is identical to the 24-amino acid segment at the N-terminal of adrenocorticotropic hormone. It is intended for use as a diagnostic agent in the screening of patients presumed to have adrenocortical insufficiency. Cosyntropin may bind to sites located on the adrenergic nerve endings associated with the cardiac tissue, and such binding would interfere with the neuronal reuptake of the catecholamines

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.

Aviptadil, a vasoactive intestinal polypeptide, is a vasodilator and lowers blood pressure if administered intravenously. In 2007, the orphan designation was granted by the European Commission for aviptadil for the treatment of sarcoidosis, a disease of unknown cause that affects many organs and tissues, most commonly the lungs. Sarcoidosis is characterized by specific microscopic lesions called granulomas. Aviptadil is able to influence the immune system that decreases the inflammatory processes seen in sarcoidosis by acting on the white blood cells (lymphocytes and monocytes) involved in the formation of the granulomas. In combination with phentolamine, the drug is used to treat erectile dysfunction. In addition, aviptadil has been studied in phase II clinical trials for patients with respiratory distress syndrome.