MSH: Chemical substances having a specific regulatory effect on the activity of a certain organ or organs. The term was originally applied to substances secreted by various ENDOCRINE GLANDS and transported in the bloodstream to the target organs. It is sometimes extended to include those substances that are not produced by the endocrine glands but that have similar effects.,CSP: chemical substances having a specific regulatory effect on the activity of a certain organ or organs, especially substances secreted by various endocrine glands and transported in the bloodstream to the target organs.,MEDLINEPLUS: Hormones are your body's chemical messengers. They travel in your bloodstream to tissues or organs. They work slowly, over time, and affect many different processes, including Growth and development Metabolism - how your body gets energy from the foods you eat Sexual function Reproduction Mood Endocrine glands, which are special groups of cell