Ghrelin, an acetylated peptide composed of 28 amino-acids, is an endogenous ligand for the growth hormone secretagogues receptor, GHS-R. Ghrelin is mainly produced by the X/A cells of the oxyntic glands in the stomach and, to a much lesser extent, in hypothalamus, pituitary, adrenal gland, intestine, gonads, heart, T lymphocytes, and monocytes. Ghrelin increases growth hormone secretion independently on and synergistically with somatoliberin.

Age-related modifications in the action of hormones depends on changes in the level of the receptor and effector

Hepatic stellate cells play a key role in the development of liver fibrosis that is characterized by a quantitative and qualitative changes in the composition and distribution of the extracellular matrix . Under the influence of the compounds released from damaged hepatocytes and Kupffer cells Browicz - , platelets , white blood cells and endothelial cells , there is a transition ( activation ) stellate cells quiescent cells myofibroblast phenotype .

Hepatic stellate cells (synonyms : lipocytes , perisinusoidalne liver cells , the cells accumulate lipids, Ito cells ) are located in the perisinusoidal space ( of Disse ) , and their basic morphological feature is the presence of numerous lipid vacuoles ( covering approximately 20% of the cell volume ) and long spike entangling often hepatic sinus wall . Under normal conditions , stellate cells comprise 70-80 % of the vitamin A in the body plays a key role in the metabolism of the compound.