The messenger molecule that carries instructions from its host organ to other cells in the body is known as a hormone.

Here's why:

* Hormones are chemical messengers produced by glands in the endocrine system. They travel through the bloodstream to target cells or organs, where they bind to specific receptors and trigger a response.

* Examples: Insulin (produced by the pancreas) regulates blood sugar levels, while estrogen (produced by the ovaries) influences female reproductive development.

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