Which of the following hormones would have the shortest half-life? A. Epinephrine B. Testosterone C. Cortisol D. Aldosterone
The correct answer and explanation is:
The correct answer is A. Epinephrine.
Epinephrine, also known as adrenaline, has the shortest half-life among the hormones listed. Its half-life in circulation is typically less than 2 minutes. This short duration is due to the fact that epinephrine is a catecholamine hormone, which is quickly broken down and metabolized by enzymes like monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT) in the liver and other tissues. Epinephrine acts as a rapid response hormone, triggering the “fight or flight” response during acute stress. This response requires a quick, temporary action, and thus, the body does not keep epinephrine circulating for long periods. It is released in a burst and rapidly cleared from the bloodstream to prevent prolonged effects.
On the other hand, hormones like testosterone, cortisol, and aldosterone have much longer half-lives. Testosterone, a steroid hormone, has a half-life of around 10 to 100 minutes, as it binds to carrier proteins in the blood, which slows its elimination. Cortisol, another steroid hormone, has a half-life of approximately 60 to 90 minutes, and it follows a similar pathway of being bound to corticosteroid-binding globulin (CBG) in the bloodstream. Aldosterone, which regulates sodium and potassium levels, has a half-life of about 20 minutes, and like cortisol, it is a steroid hormone that circulates bound to proteins, prolonging its activity.
In summary, the reason epinephrine has the shortest half-life is that it is a water-soluble catecholamine, which is rapidly degraded by enzymatic processes after being released from the adrenal glands. Its action is designed to be fast-acting and short-lived, providing the body with immediate responses to acute stressors.