What is the Origin of Term 22?

This term is a core concept in cellular and molecular endocrinology, established through early studies of receptor kinetics and cellular adaptation to hormonal signals. It illustrates the dynamic, self-regulating nature of hormonal signaling, which is constantly adjusting receptor density to maintain a functional set point. Understanding this process is vital for interpreting clinical scenarios where hormone levels are high but symptoms of deficiency persist.

What is the Mechanism of Term 22?

Upon sustained, high-level hormone binding, the hormone-receptor complexes are internalized into the cell via endocytosis, where they are either degraded in lysosomes or sequestered in vesicles. This process removes the receptors from the cell surface or nucleus, effectively reducing the cell's capacity to bind and respond to subsequent hormonal signals. This reduction in receptor density ultimately diminishes the overall signal transduction cascade, thereby protecting the cell from excessive stimulation and resetting the tissue's sensitivity threshold.

Term 22 ∞ Area

Term 22

Meaning

Receptor Downregulation is a fundamental cellular mechanism where the number of functional hormone receptors expressed on the surface or within a target cell decreases in response to prolonged exposure to high concentrations of the corresponding hormone. This process serves as a protective, homeostatic mechanism to prevent overstimulation and mitigate the cellular effects of chronic hormonal excess. Clinically, downregulation leads to a state of cellular resistance or insensitivity, meaning that even high levels of the hormone may fail to elicit the expected biological response, contributing to persistent symptoms.