Abstract
The mechanism of action of a hormone necessarily involves a series of steps: 1) an interaction of the hormone with some preexisting receptor molecule in or on the cell of the target tissue: 2) the interaction's influence of the receptor molecule's biological function (this is called the primary response to the hormone): and 3) the amplification of the primary response by modification of other metabolic machinery of the target tissue cells. At the present time, the primary action of any hormone is a subject of controversy. It is not known whether hormones have more than one primary action or whether one or more receptors are involved. Experiments to determine the primary action generally deal with studies concerning the amplification step of the hormone action; the primary action of the hormone is deduced or suggested by such studies.