Hormone

A hormone is a chemical released by a cell, a gland, or an organ in one part of the body that affects cells in other parts of the organism. Generally, only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one cell to another.

A variety of exogenous chemical compounds, both natural and synthetic, have hormone-like effects on both humans and wildlife. Their interference with the synthesis, secretion, transport, binding, action, or elimination of natural hormones in the body can change the homeostasis, reproduction, development, and/or behavior, just as endogenously produced hormones do.

Types of Hormone

Hormones can be classified as one of three different types, shown below with examples:

• Peptide hormones: insulin, growth hormone.
• Lipid hormones: testosterone, cortisol.
• Monoamines: tryptophan, phenylalanine.

See Also

• Neurotransmitter
• Receptor