what substances are secreted by the endocrine system?

2009-11-23T13:39:25Z

why are they similar to catalyst?

Anonymous2009-11-25T04:37:55Z

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The endocrine system is a collection of glands that secrete chemical messages we call hormones. These signals are passed through the blood to arrive at a target organ, which has cells possessing the appropriate receptor.

They have a specific shape and bring about changes like an enzyme does.