Which statement is true about endogenous ligands?

Which statement is true about endogenous ligands?

• A. Endogenous ligands are introduced from outside the body
• B. Endogenous ligands are never active
• C. Endogenous ligands are always excreted
• D. Endogenous ligands are produced within the body

Answer: (D)

Endogenous ligands are produced within the body and act as the body's own signaling molecules that bind to receptors to regulate physiological processes. This internal origin is what makes the statement true: the body synthesizes these ligands (such as neurotransmitters like serotonin or hormones like insulin) to control functions in a targeted way. They are released in response to signals and can have local or systemic effects, and they are active when they interact with their receptors. Exogenous ligands, by contrast, come from outside the body, and the fact that endogenous ligands are produced internally is what distinguishes them. They can be degraded or metabolized after signaling, but excretion isn’t the defining feature of endogenous ligands.

Endogenous ligands are produced within the body and act as the body's own signaling molecules that bind to receptors to regulate physiological processes. This internal origin is what makes the statement true: the body synthesizes these ligands (such as neurotransmitters like serotonin or hormones like insulin) to control functions in a targeted way. They are released in response to signals and can have local or systemic effects, and they are active when they interact with their receptors. Exogenous ligands, by contrast, come from outside the body, and the fact that endogenous ligands are produced internally is what distinguishes them. They can be degraded or metabolized after signaling, but excretion isn’t the defining feature of endogenous ligands.