What is the half-life of retinol-binding protein?

• A. 12 hours
• B. 1 day
• C. 2-3 days
• D. 1 week

Answer: (A)

Retinol-binding protein has a short plasma half-life because it serves as a rapid-turnover transporter of vitamin A. In humans, its half-life is about 12 hours, meaning its circulating level can rise or fall within roughly half a day in response to changes in hepatic synthesis or vitamin A status. This quick turnover is why RBP is considered a dynamic indicator of recent vitamin A status and why factors that affect liver production or zinc status can cause noticeable changes in RBP levels within a day. Longer timeframes like 24 hours, several days, or a week imply much slower turnover than what is observed with RBP, making those options less accurate.