News tagged with hormone Related topics: breast cancer , women ,
plants , estrogen , protein Hormones (from Greek ὁρμή -
"impetus") are chemicals released by cells that affect cells in
other parts of the body. Only a small amount of hormone is
required to alter cell metabolism. It is essentially a chemical
messenger that transports a signal from one cell to another. All
multicellular organisms produce hormones; plant hormones are
also called phytohormones. Hormones in animals are often
transported in the blood. Cells respond to a hormone when they
express a specific receptor for that hormone. The hormone binds
to the receptor protein, resulting in the activation of a signal
transduction mechanism that ultimately leads to cell type-
specific responses. Endocrine hormone molecules are secreted
(released) directly into the bloodstream, while exocrine
hormones (or ectohormones) are secreted directly into a duct,
and from the duct they either flow into the bloodstream or they
flow from cell to cell by diffusion in