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for your spouse or partner Biochemical agents that transmit
messages between components of living organisms. Hormones are
biochemical messengers that regulate physiological events in
living organisms. More than 100 hormones have been identified in
humans. Hormones are secreted by endocrine (ductless) glands
such as the hypothalamus, the pituitary gland, the pineal gland,
the thyroid, the parathyroid, the thymus, the adrenals, the
pancreas, the ovaries, and the testes. Hormones are secreted
directly into the blood stream, where they travel to target
tissues and modulate digestion, growth, maturation,
reproduction, and homeostasis. Hormones do not fall into any one
chemical category, but most are either protein molecules or
steroid molecules. These biological managers keep the body
systems functioning over the long term and help maintain health.
The study of hormones is called endocrinology.