Ghrelin is a specific endogenous ligand for the GHS receptor which can stimulate strong increase in circulating GH levels both in vitro and in vivo in a dose-dependent manner, Human acylated ghrelin is the major active form that can cross the blood-brain barrier, and has an effection on the activity of arcute neurones with a much stronger affinity (IC₅₀, 0.3×10^-9M) than GHSR antagonist (D-Lys3)-GHRP-6 (IC₅₀, 0.9×10^-6M)[1].

Ghrelin has effects in stimulating appetite, increasing secretion of GH and hypo-catabolism, improvement of gastrointestinal motility, increasing cardiac output, improvement of pulmonary function and anti-inflammatory effect.

Clinical applications of ghrelin in total gastrectomy, esophagectomy and neoadjuvant chemotherapy can stimulate food intake, improve guality of life scores and minimize adverse events. Recently, ghrelin as a effective approach in the management of anorexia nervosa[2],cachexia[3], BW[4] and appetite loss[5], systemic inflammatory response[6]and cancer[7]. In conclusion, ghrelin is a promising candidate for treating catabolic states and enhancing immune function in cachexia or acquired immunodeficiency syndrome, as well as for treating eating disorders such as obesity and anorexia nervosa.

References:
1. M. Traebert,* T. Riediger,? S. Whitebread,* E. Scharrer? and H. A. Schmid*. Ghrelin Acts on Leptin-Responsive Neurones in the Rat Arcuate Nucleus. Journal of Neuroendocrinology, 2002, Vol. 14, 580–586
2. Hotta M, Ohwada R, Akamizu T, Shibasaki T, Takano K, Kangawa K. Ghrelin increases hunger and food intake in patients with restricting-type anorexia nervosa: a pilot study. Endocr J. 2009;56:1119–28.
3. Nagaya N, Itoh T, Murakami S, Oya H, Uematsu M, Miyatake K, et al. Treatment of cachexia with ghrelin in patients with COPD. Chest. 2005;128:1187–93.
4. Adachi S, Takiguchi S, Okada K, Yamamoto K, Yamasaki M, Miyata H, et al. Effects of ghrelin administration after total gastrectomy: a prospective, randomized, placebo-controlled phase II study. Gastroenterology. 2010;138:1312–20.
5. Hiura Y, Takiguchi S, Yamamoto K, Kurokawa Y, Yamasaki M, Nakajima K, et al. Fall in plasma ghrelin concentrations after cisplatin-based chemotherapy in esophageal cancer patients. Int J Clin Oncol. 2012;17:316–23.
6. Cheyuo C, Jacob A, Wang P. Ghrelin-mediated sympathoinhibition and suppression of inflammation in sepsis. Am J Physiol Endocrinol Metab. 2012;302:E265–72.
7. Yoshida N, Watanabe M, Baba Y, Iwagami S, Ishimoto T, Iwatsuki M, et al. Risk factors for pulmonary complications after esophagectomy for esophageal cancer. Surg Today. 2014;44:526–32.