Scientific Glossary

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Hormesis ("that which excites") describes a biphasic dose-response curve: low stimulation is beneficial, high stimulation is harmful. Examples: low-dose radiation increases stress resistance; exercise (a metabolic stressor) improves fitness; intermittent fasting improves metabolic health. Many peptide research frameworks are based on hormetic principles — pulsatile GH secretagogue administration is studied to produce beneficial GH pulses rather than sustained supraphysiological levels. Senolytic research also applies hormetic thinking to cellular stress responses.

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Pharmacodynamics is the flip side of pharmacokinetics: what the compound does to the body. Includes receptor binding (affinity, selectivity), downstream signaling, therapeutic effects, and side effects. The PK/PD relationship links compound exposure (concentration) to observed response. Understanding PD helps explain why two compounds with similar structures may have very different biological effects.