Hormone: A chemical substance produced in the body that controls and regulates the activity of certain cells or organs. Many hormones are secreted by special glands, such as thyroid hormone produced by the thyroid gland. ... Many hormones, such as neurotransmitters, are active in more than one physical process.
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a regulatory substance produced in an organism and transported in tissue fluids such as blood or sap to stimulate specific cells or tissues into action.
a synthetic substance with a similar effect to that of an animal or plant hormone.
a person's sex hormones as held to influence behaviour or mood.
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