The chemical substances secreted by cells into the extracellular fluids that regulate metabolic function of other cells in the body are called hormones.

Here's why:

* Hormones are chemical messengers produced by specialized cells in the endocrine glands.

* They travel through the bloodstream to target cells or tissues, where they bind to specific receptors and trigger a response.

* This response can be a wide range of metabolic changes, including:

* Growth and development

* Metabolism of carbohydrates, proteins, and fats

* Reproduction

* Mood and behavior

* Stress response

Let me know if you have any other questions!