GLOSSARY

Receptor Sensitivity is receptor-system response to a given signal amount.

Membrane receptors can signal through G proteins, kinase activity or associated pathways; intracellular receptors often connect to gene regulation. A second messenger is distinct from the hormone, and one signal can engage several branches. Rapid responses and longer-term expression changes are not equivalent. A pathway's name alone cannot establish the actual magnitude of its effect on muscle, appetite or energy storage without tissue and outcome information.

Sensitivity is response to a given signal and is not identical to hormone concentration or receptor number. Receptor abundance, binding and downstream signaling can each alter response. Maximum responsiveness also differs from a shift in sensitivity. One blood value cannot describe all tissue receptors; assay type and target tissue are needed to interpret resistance or sensitivity rather than treating these as directly interchangeable concentration measurements.

AMPK, mTOR and related pathways integrate energy, amino-acid and other information; these proteins are not circulating hormones themselves. Components have different roles and tissue-dependent responses. A brief rise in an anabolic marker is not equivalent to guaranteed muscle gain. Effective training, adequate energy and protein and recovery opportunity are needed alongside molecular signaling for real outcomes rather than judging success from pathway activation alone.