What is the definition of body hormone?

Answer 1

A hormone is a chemical compound which is secreted by a gland into the blood and it is carried through blood to a distant site where it acts. Hormones can be divided into five major classes: (1) amino acid derivatives such as dopamine, catecholamines, and thyroid hormone; (2)small neuropeptides such as gonadotropin-releasing hormone (GnRH), thyrotropin-releasing hormone (TRH), somatostatin, and vasopressin; (3) large proteins such as insulin, luteinizing hormone (LH), and PTH produced by classic endocrine glands; (4) steroid hormones such as cortisol and estrogen that are synthesized from cholesterol-based precursors; and (5) vitamin derivatives such as retinoids (vitamin A) and vitamin D. A variety of peptide growth factors, most of which act locally, share actions with hormones. As a rule, amino acid derivatives and peptide hormones interact with cell-surface membrane receptors. Steroids, thyroid hormones, vitamin D, and retinoids are lipid-soluble and interact with intracellular nuclear receptors.