Hormones are signal- and messenger-molecules that regulate different bodily function. They can be produces locally and be freed from hormone producing cells into the surrounding tissue (paracrine secretion), or freed into the blood vessels (endocrine secretion).
The effects if the hormoes results from their binding to receptors, that can be located inside the cell membrane or inside the cytoplasm of a cell.
After interaction with its target molecule, a signal cascade is triggered inside the cell, which uses second messengers.
Hormone secretion is complexely regulated on the molecular level through complicated regulating circular effects.
Hormones have a limited half life as they are degenerated in the target tissues.
The human body can produce hormones in disseminated cells (clusters) or in the hormone producing organs, the endocrine glands.