Are hepatocytes endocrine cells?

Abstract

While exocrine glands secrete substances onto an epithelial surface through the ducts, endocrine glands are ductless and secrete their products directly into blood or lymph. These secretions are produced by specific cells, which either live in groups to form specific organs or tissues, called endocrine glands or endocrine organs, or scattered in other organs, such as cells secreting gastrointestinal hormones in gastrointestinal mucosa. These secretions were initially named "hormones" by two British physiologists -William Mortlock Bayliss and Ernest Henry Starling, in the early 20th century. Hormones enter target cells of distant organs through blood circulation and exert their unique biological effects through either binding with their membrane receptors to activate intracellular second messengers, such as protein kinases and calcium, or interacting with nuclear receptors, leading to changes in the expression and/or activity of target genes at the transcription and/or protein modification levels. Traditional endocrine organs are hypothalamus, pituitary gland, pineal gland, thyroid gland, parathyroid gland, adrenal gland, pancreatic islets, testis (male), and ovary (female). Due to the discovery of Leptin in 1994 and subsequent molecules such as Adiponectin and Resistin, adipose tissue, which stores triglyceride and energy, is also considered as an endocrine organ.