Terlipressin (Glypressin) is indicated for the treatment of bleeding oesophageal varices and in some countries for the treatment of hepato-renal syndrome type 1. It is a prodrug and is converted to the lysine vasopressin in the circulation after the N-triglycyl residue is cleaved by endothelial peptidases. This results in a ‘slow release’ of the vasoactive lysine vasopressin. Terlipressin exerts its action by activating V1a, V1b and V2 vasopressin receptors.

Angiotensin is a peptide hormone that causes vasoconstriction and a subsequent increase in blood pressure. It is part of the renin-angiotensin system, which is a major target for drugs that lower blood pressure. Angiotensin also stimulates the release of aldosterone, another hormone, from the adrenal cortex. Aldosterone promotes sodium retention in the distal nephron, in the kidney, which also drives blood pressure up. Angiotensin is an oligopeptide and is a hormone and a powerful dipsogen. Angiotensin I is derived from the precursor molecule angiotensinogen, a serum globulin produced in the liver. Angiotensin I is converted to angiotensin II (AII) through removal of two C-terminal residues by the enzyme angiotensin-converting enzyme (ACE), primarily through ACE within the lung (but also present in endothelial cells and kidney epithelial cells). ACE found in other tissues of the body has no physiological role (ACE has a high density in the lung, but activation here promotes no vasoconstriction, angiotensin II is below physiological levels of action). Angiotensin II acts as an endocrine, autocrine/paracrine, and intracrine hormone. Angiotensin II has prothrombotic potential through adhesion and aggregation of platelets and stimulation of PAI-1 and PAI-2. When cardiac cell growth is stimulated, a local (autocrine-paracrine) renin-angiotensin system is activated in the cardiac myocyte, which stimulates cardiac cell growth through protein kinase C. The same system can be activated in smooth muscle cells in conditions of hypertension, atherosclerosis, or endothelial damage. Angiotensin II is the most important Gq stimulator of the heart during hypertrophy, compared to endothelin-1 and α1 adrenoreceptors. Angiotensin II increases thirst sensation (dipsogen) through the subfornical organ of the brain, decreases the response of the baroreceptor reflex, and increases the desire for salt. It increases secretion of ADH in the posterior pituitary and secretion of ACTH in the anterior pituitary. It also potentiates the release of norepinephrine by direct action on postganglionic sympathetic fibers. Angiotensin II acts on the adrenal cortex, causing it to release aldosterone, a hormone that causes the kidneys to retain sodium and lose potassium. Elevated plasma angiotensin II levels are responsible for the elevated aldosterone levels present during the luteal phase of the menstrual cycle. Angiotensin II has a direct effect on the proximal tubules to increase Na+ reabsorption. It has a complex and variable effect on glomerular filtration and renal blood flow depending on the setting. Increases in systemic blood pressure will maintain renal perfusion pressure; however, constriction of the afferent and efferent glomerular arterioles will tend to restrict renal blood flow. The effect on the efferent arteriolar resistance is, however, markedly greater, in part due to its smaller basal diameter; this tends to increase glomerular capillary hydrostatic pressure and maintain glomerular filtration rate. A number of other mechanisms can affect renal blood flow and GFR. High concentrations of Angiotensin II can constrict the glomerular mesangium, reducing the area for glomerular filtration. Angiotensin II is a sensitizer to tubuloglomerular feedback, preventing an excessive rise in GFR. Angiotensin II causes the local release of prostaglandins, which, in turn, antagonize renal vasoconstriction. The net effect of these competing mechanisms on glomerular filtration will vary with the physiological and pharmacological environment. Angiotensin was independently isolated in Indianapolis and Argentina in the late 1930s (as 'angiotonin' and 'hypertensin', respectively) and subsequently characterised and synthesized by groups at the Cleveland Clinic and Ciba laboratories in Basel, Switzerland.

Linaclotide (marketed under the trade name Linzess and Constella) is a peptide agonist of the guanylate cyclase 2C (GC-C). Once linaclotide and its active metabolite binds to GC-C, it has local effect on the luminal surface of the intestinal epithelium. Activation of GC-C by linaclotide results in the intra- and extracellular increase of cyclic guanosine monophosphate concentrations (cGMP). This elevation of cGMP levels stimulates the secretion of chloride and bicarbonate into the intestinal lumen via activation of cystic fibrosis transmembrane conductance regulator (CFTR) ion channel. The metabolite of linaclotide MM-419447 (CCEYCCNPACTGC) contributes to the pharmacologic effects of linaclotide. Ultimately, linaclotide helps patients with IBS (especially with constipation) as GI transit is accelerated and the release of intestinal fluid is increased. In animal models, a decrease in visceral pain after administration of linaclotide may be observed. A decrease in the activity of pain-sensing nerves occurs as a result of an increase in extracellular cGMP. It was approved by the FDA in August 2012 for the treatment of chronic idiopathic constipation and irritable bowel syndrome with constipation (IBS-C) in adults.

Tesamorelin is an analog of human growth hormone-releasing factor (GRF). The peptide precursor of tesamorelin acetate is produced synthetically and is comprised of the 44 amino acid sequence of human GRF. In vitro, tesamorelin binds and stimulates human GRF receptors with similar potency as the endogenous GRF. GRF, also known as growth hormone-releasing hormone (GHRH), is a hypothalamic peptide that acts on the pituitary somatotroph cells to stimulate the synthesis and pulsatile release of endogenous growth hormone (GH), which is both anabolic and lipolytic. GH exerts its effects by interacting with specific receptors on a variety of target cells, including chondrocytes, osteoblasts, myocytes, hepatocytes, and adipocytes, resulting in a host of pharmacodynamic effects. Some, but not all these effects, are primarily mediated by IGF-1 produced in the liver and in peripheral tissues. Tesamorelin is the first and, so far, only treatment indicated for the reduction of excess abdominal fat in patients with HIV-associated lipodystrophy. Tesamorelin is effective in improving visceral adiposity and body image in patients with HIV-associated lipodystrophy over 26-52 weeks of treatment. Potential limitations for its use include high cost and lack of long-term safety and adherence data. Tesamorelin provides a useful treatment option for management of patients with significant lipodystrophy related to HIV infection.

Lanreotide is a medication used in the management of acromegaly and symptoms caused by neuroendocrine tumors, most notably carcinoid syndrome. It is a long-acting analog of somatostatin. It is available in several countries, including the United Kingdom, Australia and Canada, and was approved for sale in the United States by the Food and Drug Administration on August 30, 2007. Lanreotide was developed in the lab of Dr. David H. Coy, School of Medicine. Dr. Coy serves as Director of the Peptide Laboratory. Lanreotide (as lanreotide acetate) is manufactured by Ipsen, and marketed under the trade name Somatuline. The mechanism of action of lanreotide is believed to be similar to that of natural somatostatin. Lanreotide has a high affinity for human somatostatin receptors (SSTR) 2 and 5 and a reduced binding affinity for human SSTR1, 3, and 4. Activity at human SSTR 2 and 5 is the primary mechanism believed responsible for GH inhibition. Like somatostatin, lanreotide is an inhibitor of various endocrine, neuroendocrine, exocrine and paracrine functions. Lanreotide inhibits the basal secretion of motilin, gastric inhibitory peptide and pancreatic polypeptide, but has no significant effect on the secretion of secretin. Lanreotide inhibits postprandial secretion of pancreatic polypeptide, gastrin and cholecystokinin (CCK). In healthy subjects, lanreotide produces a reduction and a delay in post-prandial insulin secretion, resulting in transient, mild glucose intolerance.

Pramlintide is an analog of human amylin. Amylin is co-secreted with insulin from pancreatic beta cells and acts centrally to slow gastric emptying, suppress postprandial glucagon secretion, and decrease food intake. These actions complement those of insulin to regulate blood glucose concentrations. Amylin is relatively deficient in patients with type 2 diabetes, depending on the severity of beta-cell secretory failure, and is essentially absent in patients with type 1 diabetes. Through mechanisms similar to those of amylin, pramlintide improves overall glycemic control, reduces postprandial glucose levels, and reduces bodyweight in patients with diabetes using mealtime insulin. SYMLIN® (pramlintide acetate) is indicated for patients with type 1 or type 2 diabetes who use mealtime insulin and have failed to achieve desired glycemic control despite optimal insulin therapy.

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.

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