HORMONE

A hormone is a chemical messenger that carries a signal from one cell to another via the blood. All multicellular organisms produce hormones.

Hormonal signalling across this hierarchy involves the following:

1.Biosynthesis of a particular hormone in a particular tissue
2.Storage and secretion of the hormone
3.Transport of the hormone to the target cell(s)
4.Recognition of the hormone by an associated cell membrane or intracellular receptor protein.
5.Relay and amplification of the received hormonal signal via a signal transduction process: This then leads to a cellular response. The reaction of the target cells may then be recognized by the original hormone-producing cells, leading to a down-regulation in hormone production. This is an example of a homeostatic negative feedback loop.
6.Degradation of the hormone.