Half-life of insulin is
**Core Concept**
The half-life of a substance refers to the time it takes for the concentration of that substance to decrease by half due to biological processes such as metabolism or excretion. In the context of insulin, its half-life is a critical factor in determining its duration of action and potency.
**Why the Correct Answer is Right**
Insulin is a protein hormone that is metabolized primarily by the liver and kidneys. The half-life of insulin is approximately 4-6 minutes, which is relatively short compared to other hormones. This is because insulin is rapidly degraded by insulin-degrading enzyme (IDE), a zinc-dependent metalloprotease that breaks down insulin into smaller peptides. The rapid metabolism of insulin is essential for regulating blood glucose levels, as it allows for the rapid clearance of excess insulin from the bloodstream.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the half-life of insulin is not 1-2 minutes, which would be too short for the hormone to have any significant effect on blood glucose levels.
**Option B:** This option is incorrect because the half-life of insulin is not 1-2 hours, which would be too long for the hormone to be effective in rapidly regulating blood glucose levels.
**Option C:** This option is incorrect because the half-life of insulin is not 6-8 hours, which would be too long for the hormone to be cleared from the bloodstream.
**Clinical Pearl / High-Yield Fact**
A key clinical consideration when using insulin therapy is that the short half-life of insulin requires frequent dosing to maintain therapeutic effects. This can be challenging in clinical practice, particularly in patients with diabetes who may require multiple daily injections of insulin.
**Correct Answer: B. 5 minutes**