Examorelin (Hexarelin) is a hexapeptide (His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2) that stimulates the release of growth hormone lease through binding to the growth hormone secretagogue receptor (GHSR). Hexarelin might have direct cardiovascular actions beyond growth hormone release and neuroendocrine effects. Europeptides and Mediolanum Farmaceutici were developing examorelin for the treatment of somatotropin deficiency.

Tabimorelin is an orally active and selective growth hormone secretagogue (GHS) that was derived from growth hormone-releasing peptide-1(GHRP-1) via ipamorelin by a peptidomimetic approach. Tabimorelin inhibits both on gut and liver CYP3A4 activity. Tabimorelin has been in phase II clinical trials for the treatment of somatotropin deficiency. However, this research has been discontinued because the majority of growth hormone deficient adults did not respond to Tabimorelin.

Ibutamoren (L-163,191 MK-0677) is a spiropiperidine agonist of the ghrelin receptor and a growth hormone secretagogue. Ibutamoren mimics the actions of growth hormone releasing peptide-6 to increase serum levels of serum insulin-like growth factor-I (IGF-I). Orally active Ibutamoren was being developed by Merck & Co. for a variety of indications, including fibromyalgia, muscle wasting/weakness in patients with chronic kidney disease, Alzheimer's disease and fractures.However, there has been no recent development reported or development has been discontinued for these indications.

Anamorelin is a first-in-class, orally active ghrelin receptor agonist that binds and stimulates the growth hormone secretagogue receptor centrally, thereby mimicking the appetite-enhancing and anabolic effects of ghrelin. Anamorelin is under development by Helsinn Therapeutics for the treatment of cancer cachexia and anorexia. Anamorelin has completed phase III clinical trials for the treatment of cancer cachexia and anorexia associated with non-small-cell lung carcinoma. Results of the studies were positive, and the drug is now in preregistration with the European Medicines Agency.

Growth hormone releasing hexapeptide (GHRP-6) is a synthetic met-enkephalin analog that induces the release of growth hormone in vivo through binding of the ghrelin receptor. GHRP-6 increases proliferation in astrocytes through a mechanism that involves PI3K/Akt signaling. GHRP-6 also inhibits development of restraint stress-induced gastric lesions and reverses ovariectomy-induced effects on serum glucose and insulin levels. Additionally, GHRP-6 decreases locomotor activity and increases food intake in vivo. Essentially a synthetic version of ghrelin analogue, GHRP-6 (like GHRP-2) stimulates the release of an endogenous growth hormone (GH) within the somatotropes of the anterior pituitary in the animal and human body. Specifically, GHRP-6 will increase the number of somatotropes in a GH pulse by limiting the amount of somatostatin present, while standard GHRH increases the amplitude at which the pituitary cells pulse. Unlike ghrelin, GHRP-6 is not specifically used to increase appetite, but it may have secondary actions that impact hypothalamic neurons. These effects last for approximately an hour after the initial application, which mimics the natural application of GH, and consists of an eight hour circulation period. In studies GHRP-6 has shown biological actions similar to the naturally occurring hunger stimulating peptide ghrelin. Its main use is to promote food intake by stimulating hunger and aid in energy metabolism. It can be used in the treatment of GH deficiency as well as cachexia, eating disorders and obesity. GHRP-6 is a synthetic met-enkephalin (a naturally occurring opioid growth factor) analog. GHRP-6 contains D-amino acids that are entirely synthetic, lacks opioid activity, and shares no sequence relation with GHRH. It has also been shown that GHRP-6 can lead to re-stimulation of the natural production of HGH. Studies have shown that GHRP-6 increases the secretion of IGF-1 (InsulinLike Growth Factor 1) by the liver, which is speculated to be a required component in the anabolic mechanisms leading to the action of HGH. It also appears that GHRP-6 has positive implications for the central nervous system, as ghrelin is known to protect neurons.

Macimorelin (AEZS 130) is an orally active, small-molecule, peptidomimetic growth hormone secretagogue receptor (GHSR1A) agonist (ghrelin analogue), being developed by AEterna Zentaris for the diagnosis of adult growth hormone deficiency (AGHD; somatotropin deficiency), and for the treatment of cachexia associated with chronic disease such as AIDS and cancer. Macimorelin was approved by the FDA in December 2017 under the market name Macrilen for oral solution. Macimorelin stimulates GH release by activating growth hormone secretagogue receptors present in the pituitary and hypothalamus. Macimorelin has been granted orphan drug designation by the FDA for diagnosis of AGHD.

Capromorelin is a potent ghrelin receptor agonist. Capromorelin is indicated for appetite stimulation in dogs. Plasma insulin-like growth factor-I (IGF-I) was elevated progressively over a 5-d course of daily oral dosing in dogs. In healthy older adults at risk for functional decline, administration of the capromorelin may improve body composition and physical function. Adverse events included fatigue, insomnia, and small increases in fasting glucose, glycosylated hemoglobin, and indices of insulin resistance.

Pralmorelin [GPA 748, GHRP 2, growth hormone-releasing peptide 2, KP-102 D, KP 102 LN] is an orally active, synthetic growth hormone-releasing peptide from a series of compounds that were developed by Polygen in Germany and Tulane University in the US. The use of pralmorelin as a diagnostic agent for GH deficiency is based on its ability to markedly increase plasma levels of GH in healthy subjects irrespectively of gender, obesity or age. However, in patients with GH deficiency, the effect of pralmorelin on GH levels is significantly lower compared with healthy controls. Pralmorelin is marketed under the brand name GHRP in Japan. It is used as a diagnostic agent in a single-dose formulation for the assessment of growth hormone deficiency (GHD). Pralmorelin (GHRP-2) acts to endogenously increase growth hormone release from the pituitary. With the increase of serum growth hormone, downstream effects occur. A notable hormone that is commonly used as a surrogate for growth hormone therapy, insulin like growth factor 1 (IGF-1), is known to increase with the infusion of GHRP-2. Administration of GHRP-2 results in amplification of the naturally occurring growth hormone secretion peaks, regulated by the hypothalamus and pituitary. After the release of growth hormone, a cascade of signaling events occurs in many body tissues, continuous exposure to growth hormone elicits long-term physiological changes. Of particular interest, especially in the case of the use of GHRP-2 as an alternative growth hormone therapy, hepatic production of IGF-1 occurs as result of endogenously released growth hormone from GHRP-2. GHRP-2 acts on the growth hormone secretagogue receptor (GHSR1a) in pituitary and hypothalamic tissues. The growth hormone secretagogue receptor (GHSR) is the natural receptor for the endogenous hormone Ghrelin, a stress hormone produced mainly by the lining of the stomach. This receptor among many other functions, controls and growth hormone release.

Ibutamoren (L-163,191 MK-0677) is a spiropiperidine agonist of the ghrelin receptor and a growth hormone secretagogue. Ibutamoren mimics the actions of growth hormone releasing peptide-6 to increase serum levels of serum insulin-like growth factor-I (IGF-I). Orally active Ibutamoren was being developed by Merck & Co. for a variety of indications, including fibromyalgia, muscle wasting/weakness in patients with chronic kidney disease, Alzheimer's disease and fractures.However, there has been no recent development reported or development has been discontinued for these indications.