3 concepts
Direct Gene Activation and the Second-Messenger System
Nuclear receptors function as transcription factors because they can bind to DNA and regulate gene expression.
Target Cell Specificity
Hormones target a limited number of cells (based on the presence of a specific receptor) as they circulate in the bloodstream.
Onset, Duration, and Half-Life of Hormone Activity
A hormone's half-life and duration of activity are limited and vary from hormone to hormone.