A hormone, such as insulin or estrogen, is a substance released by an organ or tissue that controls the activity of organs or cells in another part of the body. The organs or glands that release hormones are part of the endocrine system.

Hormones may also be taken as medicines, such as birth control pills or estrogen replacement therapy.

Current as of: November 14, 2014

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Brian D. O'Brien, MD - Internal Medicine & Alan C. Dalkin, MD - Endocrinology