Final answer:
The half-life in hormone activity refers to the time for half the concentration of the hormone to be broken down. Steroid hormones have longer half-lives due to protein-bound transportation, exemplified by cortisol's 60 to 90-minute half-life, compared to the shorter half-life of amino acid-derived hormones like epinephrine.
Step-by-step explanation:
In the context of hormone activity, the term half-life refers to the time required for half the concentration of the hormone to be degraded or metabolized.
Steroid hormones, which are lipid-derived and hydrophobic, usually have a longer half-life because they travel in the blood bound to transport proteins, extending their duration of action. For instance, cortisol, a lipid-derived hormone, has a half-life of approximately 60 to 90 minutes.
Conversely, epinephrine, which is derived from amino acids, has a half-life of only about one minute, due to its different structure and interaction with the metabolism.
The concept of half-life is crucial in understanding not only the persistence of hormone activity in the bloodstream but also the dosing frequency needed when administering hormone-based medications.
This concept aligns with how half-lives are considered in radioactive decay, where it represents the time it takes for half of the radioactive nuclei to decay.